Valentina Penza's research while affiliated with University of Rome Tor Vergata and other places

... Furthermore, a point of great interest in this respect is represented by the observed phase and shape differences between the solar cycle and the one observed in solar wind parameters, as above discussed. Indeed, since the first evidence by Hirshberg (1973), the existence of a time lag has been subsequently confirmed in different papers (see e.g., Intriligator, 1974;Köhnlein, 1996;Li et al., 2016;Venzmer & Bothmer, 2018;Samsonov et al., 2019;Reda et al., 2022), considering different activity proxies. This time-shift could probably be connected to the peak of solar wind High Speed Streams (HSS) from Corotating Interaction Regions (CIRs) during the declining phase of the solar cycle (Tsurutani et al., 2006), when a rise in the number of geomagnetic storms is also observed (Gonzalez et al., 1990). ...

... If we factor out the I q terms, we obtain where core and wing are the relative contrasts of the intensity at the core and in the wings, respectively, between facular and quiet regions, and Mg II q is the value of the index during a period of minimum. Following Penza et al. (2022), we treat core and wing as free parameters and derive them by fitting the Mg II(t) Mg II q expression with the Bremen Mg II composite ...

... However, some recent studies have considered the even/odd cycle parity in the context of sunspot cycle prediction (e.g. Du, 2020;Kakad & Kakad, 2021;Penza et al., 2021;Du, 2022b;Nagovitsyn & Ivanov, 2023). Here we study the prediction of sunspot cycles accounting for the 22-year Hale cycle by considering the differences in the even-and odd-numbered sunspot cycles. ...

... The spot contribution to solar Ca II H and K variability is believed to be small (Shapiro et al. 2014;Sowmya et al. 2021, hereafter Paper I) because plages are very bright in Ca II H and K lines (e.g., see Figure 1 of Skumanich et al. 1984) and on the Sun their area coverages are significantly larger than that of spots. As a result, solar Ca II H and K emission is even often considered as a proxy of facular contribution to solar irradiance variability (Lean 2000;Walton et al. 2003;Chapman et al. 2013;Berrilli et al. 2020). However, the role of spots in Ca II H and K variability of other stars has not been investigated before. ...

... In order to understand the processes driving the observed variability, we compare observational results with variability obtained from an irradiance reconstruction model based on a semiempirical approach. In such approaches (e.g., Penza et al. 2006;Ermolli et al. 2011;Fontenla et al. 2011;Haberreiter et al. 2014;Criscuoli et al. 2018), the irradiance is reconstructed by combining the daily variations of area coverage of quiet and magnetic regions with synthetic spectra representing the radiative emission of the various features. Synthetic spectra are typically derived by using 1D static atmospheric models, although models based on the use of 3D radiative magnetohydrodynamic simulations of the solar atmosphere have been recently developed (Yeo et al. 2017b;Criscuoli 2020). ...

... Since the scattering is more sensitive in the UV wavelength range, surface microroughness will be accurately investigated. The SEE science team will define the scientific requirements and the related technical requirements for the detailed design of the SEE UV imager based also on the heritage of the design of the ISODY payload which included tunable interferometric filters (Berrilli et al., 2011) proposed for the ADAHELI solar mission (Berrilli et al., , 2015. ...