Exploring the Effects of Active Magnetic Drag in a Gener\al Circulation Model of the Ultrahot Jupiter WASP-76b

Ultrahot Jupiters represent an exciting avenue for testing extreme physics and observing atmospheric circulation regimes not found in our solar system. Their high temperatures result in thermally ionized particles embedded in atmospheric winds interacting with the planet’s interior magnetic field by generating current and experiencing bulk Lorentz force drag. Previous treatments of magnetic drag in 3D general circulation models (GCMs) of ultrahot Jupiters have mostly been uniform drag timescales applied evenly throughout the planet, which neglects the strong spatial dependence of these magnetic effects. In this work, we apply our locally calculated active magnetic drag treatment in a GCM of the planet WASP-76b. We find the effects of this treatment to be most pronounced in the planet’s upper atmosphere, where strong differences between the day and night side circulation are present. These circulation effects alter the resulting phase curves by reducing the hot spot offset and increasing the day–night flux contrast. We compare our models to Spitzer phase curves, which imply a magnetic field of at least 3 G for the planet. We additionally contrast our results to uniform drag timescale models. This work highlights the need for more careful treatment of magnetic effects in atmospheric models of hot gas giants.

The nighttime ionospheric response and occurrence of equatorial plasma irregularities during geomagnetic storms: a case study

Recent studies revealed that the long-lasting daytime ionospheric enhancements of Total Electron Content (TEC) were sometimes observed in the Asian sector during the recovery phase of geomagnetic storms (e.g., Lei (J Geophys Res Space Phys 123: 3217–3232, 2018), Li (J Geophys Res Space Phys 125: e2020JA028238, 2020). However, they focused only on the dayside ionosphere, and no dedicated studies have been performed to investigate the nighttime ionospheric behavior during such kinds of storm recovery phases. In this study, we focused on two geomagnetic storms that happened on 7–8 September 2017 and 25–26 August 2018, which showed the prominent daytime TEC enhancements in the Asian sector during their recovery phases, to explore the nighttime large-scale ionospheric responses as well as the small-scale Equatorial Plasma Irregularities (EPIs). It is found that during the September 2017 storm recovery phase, the nighttime ionosphere in the American sector is largely depressed, which is similar to the daytime ionospheric response in the same longitude sector; while in the Asian sector, only a small TEC increase is observed at nighttime, which is much weaker than the prominent daytime TEC enhancement in this longitude sector. During the recovery phase of the August 2018 storm, a slight TEC increase is observed on the night side at all longitudes, which is also weaker than the prominent daytime TEC enhancement. For the small-scale EPIs, they are enhanced and extended to higher latitudes during the main phase of both storms. However, during the recovery phases of the first storm, the EPIs are largely enhanced and suppressed in the Asian and American sectors, respectively, while no prominent nighttime EPIs are observed during the second storm recovery phase. The clear north–south asymmetry of equatorial ionization anomaly crests during the second storm should be responsible for the suppression of EPIs during this storm. In addition, our results also suggest that the dusk side ionospheric response could be affected by the daytime ionospheric plasma density/TEC variations during the recovery phase of geomagnetic storms, which further modulates the vertical plasma drift and plasma gradient. As a result, the growth rate of post-sunset EPIs will be enhanced or inhibited.

Far ultraviolet airglow remote sensing measurements on Feng Yun 3D meteorological satellite

The Ionospheric Photometer (IPM) is carried on the Feng Yun 3D (FY3D) meteorological satellite, which allows for the measurement of far-ultraviolet (FUV) airglow radiation in the thermosphere. IPM is a compact and high-sensitivity nadir-viewing FUV remote sensing instrument. It monitors 135.6 nm emission in the night-side thermosphere and 135.6 nm and N2 LBH emissions in the day-side thermosphere that can be used to invert the peak electron density of the F2 layer (NmF2) at night and O / N2 ratio in the daytime, respectively. Preliminary observations show that the IPM could monitor the global structure of the equatorial ionization anomaly (EIA) structure around 2:00 local time using OI 135.6 nm nightglow properly. It could also identify the reduction of O / N2 in the high-latitude region during the geomagnetic storm of Aug. 26, 2018. The IPM derived NmF2 accords well with that observed by 4 ionosonde stations along 120° E with a standard deviation of 26.67 %. Initial results demonstrate that the performance of IPM meets the designed requirement and therefore can be used to study the thermosphere and ionosphere in the future.

Magnetospheric response to the interaction with the sporadic solar wind diamagnetic structure

We report the results of a study on the movement of the solar wind diamagnetic structure (DS), which is a sequence of smaller-scale microDS being part of the May 18, 2013 coronal mass ejection, from a source on the Sun to Earth’s surface. DS determined from the high negative correlation coefficient (r=–0.9) between the IMF modulus (B) and the SW density (N) on the ACE and Wind satellites at the L1 point, on the THB and THC satellites (r=–0.9) in near-Earth orbit, and on the THA satellite inside the magnetosphere is carried by the solar wind from the Sun to Earth’s orbit, while maintaining its fine internal structure. Having a large size in the radial direction (≈763 Rᴇ, where Rᴇ is the Earth radius), DS flows around the magnetosphere. At the same time, microDS of size ≤13 Rᴇ passes through the bow shock and magnetopause as a magnetized plasmoid in which the ion concentration increases from 10 cm⁻³ to 90 cm⁻³, and the velocity decreases as it moves toward the magnetotail. When a microDS passes through the magnetopause, a pulsed electric field of ~400 mV/m is generated with subsequent oscillations with a period of T~200 s and an amplitude of ~50 mV/m. The electric field accelerates charged particles of the radiation belt and produces modulated fluxes of protons in an energy range 95–575 keV on the day side and electrons in 40–475 keV and protons in 95–575 keV on the night side. In the duskside magnetosphere (19–23 MLT), the substorm activation is observed in geomagnetic pulsations and auroras, but without a magnetic negative bay. In the post-midnight sector (01–05 MLT), a sawtooth substorm occurs without the growth phase and breakup with deep modulation of the ionospheric current and auroral absorption. The duration of all phenomena in the magnetosphere and on Earth is determined by the period of interaction between DS and the magnetosphere (~4 hrs). To interpret the regularities of the magnetospheric response to the interaction with DS, we consider alternative models of the impulsive passage of DS from SW to the magnetosphere and the classical model of reconnection of IMF and the geomagnetic field.

Magnetospheric response to the interaction with the sporadic solar wind diamagnetic structure

We report the results of a study on the movement of the solar wind diamagnetic structure (DS), which is a sequence of smaller-scale microDS being part of the May 18, 2013 coronal mass ejection, from a source on the Sun to Earth’s surface. DS determined from the high negative correlation coefficient (r=–0.9) between the IMF modulus (B) and the SW density (N) on the ACE and Wind satellites at the L1 point, on the THB and THC satellites (r=–0.9) in near-Earth orbit, and on the THA satellite inside the magnetosphere is carried by the solar wind from the Sun to Earth’s orbit, while maintaining its fine internal structure. Having a large size in the radial direction (≈763 Rᴇ, where Rᴇ is the Earth radius), DS flows around the magnetosphere. At the same time, microDS of size ≤13 Rᴇ passes through the bow shock and magnetopause as a magnetized plasmoid in which the ion concentration increases from 10 cm⁻³ to 90 cm⁻³, and the velocity decreases as it moves toward the magnetotail. When a microDS passes through the magnetopause, a pulsed electric field of ~400 mV/m is generated with subsequent oscillations with a period of T~200 s and an amplitude of ~50 mV/m. The electric field accelerates charged particles of the radiation belt and produces modulated fluxes of protons in an energy range 95–575 keV on the day side and electrons in 40–475 keV and protons in 95–575 keV on the night side. In the duskside magnetosphere (19–23 MLT), the substorm activation is observed in geomagnetic pulsations and auroras, but without a magnetic negative bay. In the post-midnight sector (01–05 MLT), a sawtooth substorm occurs without the growth phase and breakup with deep modulation of the ionospheric current and auroral absorption. The duration of all phenomena in the magnetosphere and on Earth is determined by the period of interaction between DS and the magnetosphere (~4 hrs). To interpret the regularities of the magnetospheric response to the interaction with DS, we consider alternative models of the impulsive passage of DS from SW to the magnetosphere and the classical model of reconnection of IMF and the geomagnetic field.

The ultra-hot-Jupiter KELT-16 b: Dynamical Evolution and Atmospheric Properties

We present broad-band photometry of 30 planetary transits of the ultra-hot Jupiter KELT-16 b, using five medium-class telescopes. The transits were monitored through standard B, V, R, I filters and four were simultaneously observed from different places, for a total of 36 new light curves. We used these new photometric data and those from the TESS space telescope to review the main physical properties of the KELT-16 planetary system. Our results agree with previous measurements but are more precise. We estimated the mid-transit times for each of these transits and combined them with others from the literature to obtain 69 epochs, with a time baseline extending over more than four years, and searched for transit time variations. We found no evidence for a period change, suggesting a lower limit for orbital decay at 8 Myr, with a lower limit on the reduced tidal quality factor of $Q^{\prime }_{\star }>(1.9 \pm 0.8) \times 10^5$ with $95\%$ confidence. We built up an observational, low-resolution transmission spectrum of the planet, finding evidence of the presence of optical absorbers, although with a low significance. Using TESS data, we reconstructed the phase curve finding that KELT-16 b has a phase offset of 25.25 ± 14.03 ○E, a day- and night-side brightness temperature of 3190 ± 61 K and 2668 ± 56 K, respectively. Finally, we compared the flux ratio of the planet over its star at the TESS and Spitzer wavelengths with theoretical emission spectra, finding evidence of a temperature inversion in the planet’s atmosphere, the chemical composition of which is preferably oxygen-rich rather than carbon-rich.

Atmospheres of lava exoplanets. Where and what to look for.

<p>Strongly irradiated rocky planets will have sufficiently high surface temperatures to sustain dayside magma lakes and oceans that will outgas low-pressure days-side silicate atmospheres. The surface magma will preferentially outgas its most volatile components and eventually equilibrate itself with the formed atmosphere. However, the volatile constituents may be depleted due to transport and condensation to the cooler night side or escape to space. If the atmospheric evolution is slower than the surface-interior exchange, the melt composition will remain coupled with the planet's interior. In such a case the atmospheric component will be continuously replenished. If atmospheric evolution is fast, the magma pool will lose its volatile component and the atmospheric composition will be irreversibly changed. We employ numerical models of outgassing, atmospheric chemistry, and radiative transfer to model the possible observable emission features of evolving magma atmospheres for all confirmed rocky lava worlds. . Our results highlight the best possible observable features in the atmospheres of hot rocky exoplanets that may give insight in their interior and atmospheric evolution. We also propose a set of ideal targets for JWST and ARIEL missions.<br><br><br></p>

A new type of cloud discovered from Earth in the upper Martian atmosphere

<p>During the 2020 Mars opposition, we observe from Earth the occurrence of a non-typical large-scale high-altitude clouds system, extending over thousands of km from the equator to 50°S. Over 3 hours, they emerge from the night side at an altitude of 90 (-15/+30) km and progressively dissipate in the dayside. They occur at a solar longitude of 316°, west of the magnetic anomaly and concomitantly to a regional dust storm. Despite their high altitude, they are composed of relatively large particles, suggesting a probable CO<sub>2</sub> ice composition, although H<sub>2</sub>O cannot be totally excluded. Such ice clouds were not reported previously. We discuss the formation of this new type of clouds and suggest a possible nucleation from cosmic particle precipitation.</p>

The terrestrial radiation belts as seen by BepiColombo during its flyby to Earth

<p>BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury, that was launched in October 2018 and it is due to arrive at Mercury in late 2025. It consists of two spacecraft, the Mercury Planetary Orbiter (MPO) built by ESA, and the Mercury Magnetospheric Orbiter (MMO) built by JAXA, as well as a Mercury Transfer Module (MTM) for propulsion built by ESA. The cruise phase to Mercury will last ~7 years and constitutes an exceptional opportunity for studying the evolution of the solar wind, solar transients, as well as for planetary science and planetary space weather. Some important aspects to consider during the cruise are the close distances to the Sun that BepiColombo will face, the near half-solar activity cycle that will cover, as well as the several flybys to Earth, Venus and Mercury that will perform. So far, BepiColombo has accomplished a flyby to Earth in April 2020 and a flyby to Venus in October 2020, with a second flyby to Venus programmed for August 2021 and the first Mercury flyby in October 2021.</p><p>This work focuses on the flyby to Earth, and in particular, on the radiation belt observations performed by several instruments onboard BepiColombo. The flyby occurred on 10 April 2020 under relatively steady solar wind conditions. BepiColombo crossed the outer radiation belt on the terrestrial dawn side when moving from the day side to the night side. It skimmed the inner radiation belt on the night side sector after dawn, and then crossed again the outer belt at night (behind the dusk terminator region). Two instruments onboard the MPO spacecraft were able to take measurements of the belts: the BepiColombo Radiation Monitor (BERM) and the Solar Intensity X-Ray and Particle Spectrometer (SIXS). In this work, we report the particle species, radiation and energies observed by these two instruments, as well as we perform a cross-calibration of their detections, which is an important activity in preparation for joint-observations of the Hermean environment. Moreover, using magnetic field observations from MPO-MAG, we also investigate the trajectory of the particles within the radiation belts. This work is complemented with data from other missions that give us the state of the terrestrial system and frame our observations into the right context. It includes data from Cluster-II, Themis, and Arase/ERG missions.</p>