Space Climate: Radiation, Particles, and Responses

Evaluating F10.7 and F30 radio fluxes as long-term solar proxies of energy deposition in the thermosphere

whawkins — Tue, 25 Feb 2025 16:24:07 +0000

Evaluating F10.7 and F30 radio fluxes as long-term solar proxies of energy deposition in the thermosphere whawkins Tue, 02/25/2025 - 09:24

Author:

whawkins

Feb 25, 2025

Annale Geophsicae: We use model simulations and observations to examine how well the F10.7 and F30 solar radio fluxes have represented solar forcing in the thermosphere during the last 60 years of weakening solar activity. We found that increased saturation of radio fluxes during the last two extended solar minima leads to an overestimation of solar energy deposition, which manifests as a change in the linear relation between thermospheric parameters and F10.7. On the other hand, the linear relation between thermospheric parameters and F30 remains nearly the same throughout the whole studied period because of a recently found relative increase of F30 with respect to F10.7. This explains the earlier finding that F30 correlates better with several ionospheric and thermospheric parameters than F10.7 during recent decades. We note that continued evaluation is needed to see how well F10.7 and F30 will serve as solar proxies in the future when solar activity may start increasing toward the next grand maximum.

Averaged mass density at 400 km. Black: mass density derived from satellite drag data; blue: simulated mass density using F10.7 as a solar EUV proxy; red: simulated mass density using F30 as a solar EUV proxy. (b) Solid black: mass density ratio of the simulated density using F10.7 as a solar EUV proxy to the density derived from satellite drag; dotted red line: linear fit to the mass density ratio from 1967–1996; dotted black line: linear fit to the mass density ratio from 1967–2019; blue: daily F10.7 for reference. (c) Same as panel (b) but for the case with the simulated mass density using F30 as a solar EUV proxy.

A Magnetohydrodynamic Mechanism for the Formation of Solar Polar Vortices

whawkins — Wed, 13 Nov 2024 16:03:34 +0000

A Magnetohydrodynamic Mechanism for the Formation of Solar Polar Vortices whawkins Wed, 11/13/2024 - 09:03

Author:

whawkins

Nov 13, 2024

PNAS (Proceedings of National Academy of Sciences): Polar vortices are ubiquitous features of planetary atmospheric flows, from the Earth-like rocky planets to Jupiter- and Saturn-like gas giant planets. Very little is known about their existence or dynamics on the Sun. What should be expected near the Sun’s pole for the upcoming solar multi-viewpoint and polar missions? Here we report the first magnetohydrodynamic nonlinear simulations for the formation and evolution of solar polar vortices using a near-surface magnetohydrodynamic shallow-water model. Our findings indicate that the rush-to-the-poles, the migration of magnetic fields towards the pole following the Sun’s magnetic cycle, can positively contribute to the formation of polar vortices. The mechanism proposed here for the formation of polar vortices is the first one to involve the role of magnetic fields and may be relevant to any star with a magnetic cycle. The Sun’s polar vortices resulting from this mechanism are predominantly magnetohydrodynamic, consisting of a tight pair of cyclonic and anticyclonic swirls. This mechanism is likely to operate during all solar cycle phases except the peak, when the polar field reverses. Polar vortices can impact dynamical evolution of global flows and polar fields, which seed the next activity cycle, hence better knowledge of physics of polar regions may lead to improved solar cycle and space weather forecasts. See: NSF-NCAR news website.

Simulations of magnetohydrodynamically governed polar vortices for a 30-degree inclined view (left) and for a polar view (right). Magnetohydrodynamic simulations show that the initial mid-latitude perturbations tend to drift and cluster around the forming multiple complex cyclonic and anticyclonic swirls. Following the polar rush, these swirls ultimately lead to an evolved configuration consisting of a pair of tight swirls with m=1 pattern.

Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended

whawkins — Fri, 02 Feb 2024 22:11:17 +0000

Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended whawkins Fri, 02/02/2024 - 15:11

Author:

whawkins

Feb 2, 2024

Five-year zonal mean decadal value differences relative to the 1920s at March equinox (top) and June solstice (bottom) for neutral temperature on the 2.84×10-8 hPa pressure surface a) at ~295 km and e) at ~285 km, neutral density b) at ~377 km and f) at ~395 km, electron density c) at ~377 km and g) at ~395 km, and d) and h) electron column density.

Journal of Geophysical Research, Atmospheres: From seeing lower atmosphere computer climate models run for the past century, we decided to do the same for the upper atmosphere using the Whole Atmosphere Community Climate Model-eXtended (WACCM-X) for the decades from the 1920s to 2010s. In this higher region, the atmosphere is affected strongly by the Sun and removing the Sun’s effect is tricky in previous observation and model studies. We make the Sun’s effect small to see only effects from the Earth’s magnetic field and greenhouse gases. Earlier studies focused on recent decades show effects of greenhouse gas increases on the upper atmosphere but not for the early decades of the past century with greenhouse gas changes from less than 5% increase prior to the space age and the transition to the over 25% increase in the latter half of the 20th century. We cover this entire period and get results like those in studies before, with especially the temperature change matching very well with the greenhouse gas carbon dioxide change. Because WACCM-X performs well over the past century, it will be useful to predict what will happen in the century ahead as greenhouse gases increase and humans make efforts to reverse the increase.

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021

whawkins — Tue, 27 Jun 2023 20:31:42 +0000

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021 whawkins Tue, 06/27/2023 - 14:31

Author:

whawkins

Jun 27, 2023

Geophysical Research Letters: During the storm on November 3 to 4, 2021, the Global-scale Observations of the Limb and Disk (GOLD) mission observed well separated EIA crests post sunset on Nov 3, but merged EIA on Nov 4. We used the Whole Atmosphere Community Climate Model (WACCM-X) to simulate the EIA structures during the two nights. The simulations show two separated post sunset EIA crests on November 3rd but merged post sunset EIA crests on November 4th, which are qualitatively consistent with the GOLD observations. Numerical simulations and Ionospheric Connection Explorer (ICON) neutral wind observations illustrate that the formation of merged EIA crests was due to several hours of downward E × B drifts before and after sunset. Further diagnostic analysis revealed that it was mainly driven by westward electric fields caused by the disturbance dynamo electric field during the recovery phase of the storm.

Nmax observed by GOLD and NmF2 simulated by WACCM-X at 20:10 UT on November 03-04, 2021. The red dotted lines represent the magnetic equator.

Space Climate: Radiation, Particles, and Responses

Evaluating F10.7 and F30 radio fluxes as long-term solar proxies of energy deposition in the thermosphere

Recent News

A Magnetohydrodynamic Mechanism for the Formation of Solar Polar Vortices

Recent News

Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended

Recent News

Investigation of the GOLD Observed Merged Nighttime EIA with WACCM-X Simulations during the Storm of November 3–4, 2021

Recent News