Masashi Kamogawa

University of Shizuoka · Global Center for Asian and Regional Research

We present a catalog of 525 sprites detected over the Sea of Japan and a northeast part of the Pacific Ocean from Sagamihara between September 2016 and March 2021. We analyze the morphology of 525, estimate the location of 441, and calculate the accurate top height of 15 sprites. More than half of our samples occurred in winter, while only 11% were...

We present a novel method to discriminate atmospheric electric field (AEF) variations originating from the global electrical circuit and local meteorological‐induced AEF variations. By comparing the AEF values measured at two different heights, the method identifies the AEF data including disturbances caused by charged blowing snow particles, and p...

Transient luminous events (TLEs) are electrical discharges in the upper atmosphere caused by vigorous thunderstorms. Six sprites, which are part of TLEs, were observed on 22 July 2013 from Mt. Fuji (3776 m above sea level), Japan. All the six sprites were associated with intense positive cloud-to-ground strikes (+CGs), whose causative positive char...

Five sprites produced above the stratiform region and one sprite above the convective region in the mesoscale convective system (MCS) were observed on 22 July 2013 from the summit of Mt. Fuji. Four of the five sprites occurred in the stratiform region after the stratiform region was cut off from the convective region. The five sprite-producing +CGs...

We develop a new method to analyze the total electron content (TEC) depression in the ionosphere after a tsunami occurrence. We employ Gaussian process regression to accurately estimate the TEC disturbance every 30 s using satellite observations from the global navigation satellite system (GNSS) network, even over regions without measurements. We f...

Lightning observation system was developed by measuring the current flowing through the grounding conductor connected to the foot of the Mt. Fuji from the summit. From the current measurement, the type of lightning and leader was identified such as negative cloud-to-ground lightning striking into the weather station, upward leader lightning, and st...

Crustal deformation due to the 2016 earthquake sequence in Kumamoto, Japan, that culminated in a preceding earthquake of magnitude M6.5 and a subsequent M7.3 earthquake 28 h later, caused stress perturbation on and around the causative Futagawa-Hinagu fault zone. Monitoring changes in seismicity pattern along this zone plays a role in understanding...

There is an atmospheric electric field (AEF) or an electric potential gradient (PG) in fair weather between the Earth's surface and the mesosphere/ionosphere, which is positive. During blizzards/snowstorms in the polar regions, an intense positive AEF/PG in the order of 10³ V/m of the same polarity in fair weather was observed using an electric fie...

We develop a new method to analyze the total electron content (TEC) depression in the ionosphere after a tsunami occurrence. We employ Gaussian process regression to accurately estimate the TEC disturbance every 30 s using satellite observations from the GNSS network, even over regions without measurements. We face multiple challenges. First, the i...

Preseismic VLF electromagnetic pulses occasionally increase a few days before large earthquakes, especially inland earthquakes. More than two decades ago, the Tokai University group developed a digital recording system for collecting the preseismic electromagnetic pulse data and showed remarkable results. However, due to the limitations of personal...

Crustal deformation due to the 2016 earthquake sequence in Kumamoto, Japan, that culminated in a preceding earthquake of magnitude M6.5 and a subsequence M7.3 earthquake 28 hours later, caused stress perturbation on and around the causative Futagawa-Hinagu fault zone. Monitoring changes in seismicity pattern along this zone plays a role in understa...

We report the first observations of periodic oscillations of an atmospheric electric field simultaneously derived by field mills at four observation sites at a distance of 50–65 km in metropolitan Tokyo. Oscillations were detected during a snowfall event on 23–24 November, 2016. The main period of the oscillations of the atmospheric electric field...

During 2017–2018 winter operation of the Gamma‐Ray Observation of Winter Thunderclouds experiment in Japan, two downward terrestrial gamma‐ray flashes (TGFs) that triggered atmospheric photonuclear reactions were detected. They took place during winter thunderstorms on 5 December 2017 and 9 January 2018 at Kanazawa, Ishikawa Prefecture, Japan. Each...

A highly stressed area where eventual ruptures have often been observed to nucleate is characterized by low b values of earthquake frequency‐size distribution. Crustal deformation due to the occurrence of large earthquakes causes stress perturbation in nearby regions, so an investigation into spatiotemporal b values can play a crucial role in the d...

We consider how recent regulatory requirements on units about weight, gravity, and mass, and conventions used since the adoption of the gravitational metric system, affect present meaning and the units of weight in science and mathematics at elementary schools. Measurement units and their symbols are taught using the International System of Units (...

Two types of high-energy events have been detected from thunderstorms. One is “terrestrial gamma-ray flashes” (TGFs), sub-millisecond emissions coinciding with lightning discharges. The other is minute-lasting “gamma-ray glows”. Although both phenomena are thought to originate from relativistic runaway electron avalanches in strong electric fields,...

In Japan, folklore says that uncommon appearances of deep‐sea fish are an earthquake precursor. If this folklore is proved to be true, the appearance of deep‐sea fish could be useful information for disaster mitigation. However, a statistical survey has not been conducted on this subject because a database of such information had yet to be compiled...

Lightning is an important source of nitrogen oxides (LNOx). The actual global production of LNOx is still largely uncertain. One of the reasons for this uncertainty is the limited available observation data. We measured the concentrations of total reactive nitrogen (NOy), nitric oxide (NO) and nitrogen dioxides (NO2) and then obtained NOx oxidation...

The relation between the size of an earthquake mainshock preparation zone and the magnitude of the forthcoming mainshock is different between nucleation and domino-like cascade models. The former model indicates that magnitude is predictable before an earthquake's mainshock because the preparation zone is related to the rupture area. In contrast, t...

In the summer of 2016, 14 cases of jumping cirrus (JC) were observed around the Kanto region in Japan by ground-based, visible-light cameras. The cameras were set at the summit of Mt. Fuji and National Defense Academy (Kanagawa, Japan), and 15-second time-lapse photography was continually taken for the period. The location and spatial scale of the...

We compare two observations of gamma-rays before, during, and after lightning flashes initiated by upward leaders from a tower during low-altitude winter thunderstorms on the western coast of Honshu, Japan. While the two leaders appear similar, one produced a terrestrial gamma-ray flash (TGF) so bright that it paralyzed the gamma-ray detectors whil...

We compare two observations of gamma rays before, during, and after lightning flashes initiated by upward leaders from a tower during low-altitude winter thunderstorms on the western coast of Honshu, Japan. While the two leaders appear similar, one produced a terrestrial gamma ray flash (TGF) so bright that it paralyzed the gamma ray detectors whil...

Analytical methods for the detection of NOz have been developed by using a laser-induced fluorescence spectroscopy (LIF) technique and a chemiluminescence (CL) method. NOz (= NOy – NOx) represents NOx oxidation products. The NO2 concentrations are measured by LIF, which has a high sensitivity and no chemical interferences when a conversion techniqu...

An on-ground observation program for high-energy atmospheric phenomena in winter thunderstorms along the Japan Sea has been performed via measurements of gamma ray radiation, atmospheric electric field, and low-frequency radio band. On 11 February 2017, the radiation detectors recorded gamma ray emission lasting for 75 s, and then abruptly terminat...

An on-ground observation program for high energy atmospheric phenomena in winter thunderstorms along Japan Sea has been performed via measurements of gamma-ray radiation, atmospheric electric field and low-frequency radio band. On February 11, 2017, the radiation detectors recorded gamma-ray emission lasting for 75 sec. The gamma-ray spectrum exten...

Following a lightning strike to a wind turbine in Japan, we have observed a large burst of neutrons lasting 100 ms with a ground fluence of ~1,000 n cm⁻², thousands of times greater than the peak neutron flux associated with the largest ground level solar particle event ever observed. This is the first detection of an unequivocal signature of neutr...

Ionospheric plasma disturbances after a large tsunami can be detected by measurement of the total electron content (TEC) between a Global Positioning System (GPS) satellite and its ground-based receivers. TEC depression lasting for a few minutes to tens of minutes termed as tsunami ionospheric hole (TIH) is formed above the tsunami source area. Her...

A remote-sensing payload designed for a Mars rover, to observe Martian discharge events induced by dust devils and storms, is introduced. Low-frequency electromagnetic (E-M) and acoustic wave (AW) measurements have never been performed on Mars. Thus, to date, the occurrence of large-scale electrical discharges on Mars remains unknown. These measure...

The 2016 Kumamoto earthquakes occurred under circumstance that seismicity remains high in all parts of Japan since the 2011 Tohoku-Oki earthquake. Identifying what happened before this incident is one starting point for promote earthquake forecast research to prepare for subsequent large earthquakes in the near future in Japan. Here we report precu...

A three-dimensional (3D) X-ray computed tomography (CT) instrument for radiation education was developed. The structure of the instrument is such that the main parts, i.e. the X-ray source, specimen rotation stage, and two-dimensional detector can be easily observed. An experiment using a fruit of green pepper as a specimen was performed. CT images...

Ionospheric disturbances occurred as a result of the tsunami associated with the 2011 M9.0 off the Pacific Coast of the Tohoku earthquake (EQ). The ionospheric disturbances propagated radially from the tsunami source area, termed the traveling ionospheric disturbance. In addition to the traveling ionospheric disturbance, an ionospheric plasma depre...

In fair weather, a clear diurnal variation of atmospheric electric field (AEF), which is distinctly different from the global diurnal variation, i. e., Carnegie curve, was observed during the summer time (July and August) of the year 2010 and 2011 at the summit of Mt. Fuji, Japan (3776 m in altitude). The variation of the AEF at the summit showed a...

Significance It was recently found that a few months before major earthquakes, the seismicity in the entire Japanese region exhibits a characteristic change. This change, however, can be identified when seismic data are analyzed in a new time domain termed “natural time.” By dividing the Japanese region into small areas, we find that some small are...

We propose an satellite observation to investigate preseismic lithosphere-atmosphere-ionosphere (LAI) coupling. Preliminary mission analysis shows that it is possible to prove not only a statistical correlation but also causation between earthquake and ionospheric anomaly even by three dedicated nano-satellites. The observation of proposed satellit...

Anomalous groundwater changes started three months before the 2011 M9.0 Off the Pacific coast of the Tohoku Earthquake (Tohoku EQ), Japan. Groundwater level and temperature decreased almost simultaneously in a 2000-m well at a spa, Goyo-onsen, in Iwate Prefecture, 155 km northwest of the epicenter. Since the source of Goyo-onsen, located above the...

Langmuir-Blodgett (LB) films containing azobenzene undergo reversible structural change under light irradiation because of trans-to-cis or cis-to-trans transformations of azobenzene molecules. Such films are a candidate for molecular machines. Time resolved measurements of specular X-ray reflectivity (XRR) curves were carried out for polymer specim...

The scintillation counter is a widely-used X-ray detector. It contains a scintillator as a luminescent material that converts X-rays into visible light, which is detected with a sensor. A well-known scintillator in the X-ray region is sodium iodide, NaI, an ionic crystal. Before use, it is important to understand how the detector works. For student...

In this article, we review papers on precursors for the 2011 off the Pacific coast of Tohoku Earthquake. We discuss phenomena such as seismic, geodetic, electromagnetic, ionospheric, and macroscopic anomalies for which time scales range from a few decades to a few hours, from long-, mid- to short-term precursors. Of these, we treat ionospheric anom...

There is an ionospheric potential between conductive solid-earth and ionosphere which reaches approximately 250 kV. The ionospheric potential is generated by the spherical shell capacitance of which is formed by positively charged ionosphere and negatively charged solid-earth. The capacitance is charged and discharged by the global thunderstorm act...

Measuring electron density (Ne) and temperature (Te) using a DC Langmuir probe in the ionosphere is very often degraded by the electrode contamination. In order to examine the accuracy of DEMETER observations, we compared DEMETER Ne and Te with several other satellites observations and IRI2012 as reference data. DEMETER Ne and Te show well-known de...

It has been shown that some dynamic features hidden in the time series of complex systems can be uncovered if we analyze them in a time domain called natural time χ. The order parameter of seismicity introduced in this time domain is the variance of χ weighted for normalized energy of each earthquake. Here, we analyze the Japan seismic catalog in n...

Heki [2011] reported that the TEC gradually enhanced from 40 minutes before the 2011 M9.0 off the Pacific coast of Tohoku earthquake (Tohoku EQ) to the time when the co-seismic acoustic wave reached the ionosphere and the TEC immediately recovered at the normal state. This paper shows an alternative interpretation of total electron content (TEC) va...

Coseismic ionospheric disturbances (CIDs) associated with the 2011 Tohoku earthquake off the Pacific coast (Mw 9.0, Tohoku EQ) were examined using total electron content and seismic wave data. A faster CID propagated at ~3.0 km/s only in the west-southwest, while a slower CID propagated concentrically at 1.2 km/s or slower from the tsunami source a...

We measure an atmospheric electric field inside the nonthunderstorm clouds, because the studies of the electric charge structures inside the nonthunderstorm clouds have been few. For this purpose, a balloon with a gondola equipped with two field mills was used in balloon experiments for university students (BEXUS) organized by Europe Space Agency (...

Monitoring of telluric current, which is practically a synonym for geoelectric potential difference, was conducted on Kozu-shima Island about 170 km south of Tokyo from May 14, 1997 to June 25, 2000. During the monitoring period, 19 anomalous telluric current changes (ATCs) were observed. Their possible correlation with nearby earthquakes was stati...

Traveling ionospheric disturbances generated by an epicentral ground/sea surface motion, ionospheric disturbances associated with Rayleigh-waves as well as post-seismic 4-minute monoperiodic atmospheric resonances and otherperiod atmospheric oscillations have been observed in large earthquakes. In addition, a giant tsunami after the subduction eart...

Electron density (Ne) and temperature (Te) observed by the DEMETER satellite are validated comparing with various satellites and empirical models of ionosphere/thermosphere such as Hinotori, Dynamic Explorer 2 (DE2), AE-series, and FORMOSAT3/COMSMIC, models based on satellite mass spectrometer and ground-based incoherent scatter data (the MSIS mode...

Giant earthquake and tsunami widely disturbed ionospheric plasma via acoustic gravity waves. During the M 9.0 2011 off the Pacific coast of Tohoku earthquake, the ionospheric disturbances were generated by co-seismic epicentral ground/sea surface motion, Rayleigh-wave traveling, and tsunami-wave traveling. In addition, seismo-tsunamigenic ionospher...

For the prediction of the expected Tokai Earthquake (EQ), Japan Meteorological Agency (JMA) has been observing volumetric strain changes to detect its presumed pre-slip phenomena in Tokai and South Kanto regions. In 1998, an anomalous volumetric strain change, lasting for 5 days, which initially attracted much attention as a possible precursor to t...

We identify a migrating source of high energy radiation, lasting for several minutes, attributed to thunderstorm activities through the observations of radiation, atmospheric electric field, and meteorological radar echoes at several points. Our findings indicate that the energetic radiation is emitted continuously from a downward hemispherical sur...

Transient ionospheric disturbances in the total electron content (TEC) are examined before and after the M9.0 2011 off the Pacific coast of Tohoku Earthquake to find ionospheric responses to the radiation caused by Fukushima I nuclear power plant accident, which was damaged by the earthquake and tsunamis. The TEC is derived from records of a ground...

An earthquake of magnitude 9.0 occurred near the east coast of Honshu (Tohoku area), Japan, producing overwhelming Earth surface motions and inducing devastating tsunamis, which then traveled into the ionosphere and significantly disturbed the electron density within it (hereafter referred to as seismotraveling ionospheric disturbances (STIDs)). Th...

A quantity exists by which one can identify the approach of a dynamical system to the state of criticality, which is hard to identify otherwise. This quantity is the variance κ(1)(≡<χ(2)> - <χ>(2)) of natural time χ, where <f(χ)> = Σp(k)f(χ(k)) and p(k) is the normalized energy released during the kth event of which the natural time is defined as χ...

Earthquake (EQ) prediction, in particular short-term prediction, is one of the topmost challenges in modern science. However, the general view of the community is pessimistic. EQ prediction research has been rather heavily biased toward seismology for the last several decades. In addition to seismics, however, the importance of other methods is bei...