Seiji Yashiro

The Radio-wave Observations at the Lunar Surface of the photoElectron Sheath (ROLSES) instrument is a radio telescope system designed to characterize the radio and plasma wave environment of the near-side lunar surface at frequencies between 2[Formula: see text]kHz and 30[Formula: see text]MHz. The ROLSES sensor consists of a set of four 2.5[Formula: see text]m radio monopole antennas onboard the Intuitive Machines-1 (IM-1) lander, Odysseus. The antennas were stowed during launch to be deployed after landing on the lunar surface using a frangibolt mechanism. The frequency range is well suited to observing radio waves at frequencies below 15[Formula: see text]MHz that cannot be observed from Earth due to the ionospheric cutoff. The higher frequencies are helpful in cross-calibrating with ground-based observations. Radio waves from the Sun, the Milky Way galaxy, Jupiter, Earth’s auroral region, and ground-based radio transmitters were expected to be present on the lunar surface. In addition, local plasma fluctuations and lunar/interplanetary dust were expected to produce detectable radio signals. Radio data from each of the four antennas, after passing through an isolating pre-amp and signal conditioning analog electronics, are digitized to 14 bits at 120 mega samples per second and then digitally processed by a Field Programmable Gate Array (FPGA) that performs onboard spectral analysis via a Fast Fourier Transform (FFT). Time-averaged spectral values are then stored and returned. ROLSES science data are sent to the lander at ∼16 kb/s and subsequently downlinked for further processing. Also telemetered to Earth are raw waveforms (unprocessed time sequence data) that are useful in studying dust impact on ROLSES antennas. ROLSES data are sent to the lander and subsequently downlinked for further processing. ROLSES is part of NASA’s Commercial Lunar Payload Services (CLPS) program. Odysseus landed close to the south pole at Malapert A (∼80S). This paper describes the complete design and operations of the ROLSES instrument and presents initial observations. Despite the tilted landing of Odysseus, we were able to successfully command, deploy the antennas, and operate the instrument in transit and on the lunar surface. We also describe an enhanced version of this instrument (ROLSES 2) currently under development.

We report on a writhed magnetic flux rope (MFR) eruption originating from active region 12936 located at N18E06, associated with a halo coronal mass ejection that erupted on 2022 January 29. To our knowledge, this event is among the first cases where a writhed MFR has been comprehensively observed from both solar and in situ perspectives. The Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) hot channels (94 and 131 Å) have detected a slow rise of the writhed MFR, where its western elbow (flux rope west, FRw) expands in the NW direction while the eastern elbow (flux rope east, FRe) expands in the NE direction. Using a two flux rope (FR) segment approximation, the graduated cylindrical shell (GCS) fit to EUV and white-light images yield a tilt of 29 ^∘ for FRw (pointing towards the SE) and 60 ^∘ for FRe (pointing towards the NE), indicating a writhing motion of the MFR axis. On 2022 February 2, the subsequent magnetic cloud (MC) was fortuitously intercepted by three closely spaced spacecraft: STEREO Ahead (STA, 34 . ° 6 east), Wind at the first Lagrange point, and Solar Orbiter (SolO, 18 . ° 6 east). The MC tilts obtained from Lundquist fitting agree with the GCS tilts within ∼1 ^∘ for FRw and ∼9 ^∘ for FRe. In addition, the GCS-fit propagation direction for FRw is N10E06, which is close to Wind, and for FRe is N09E26, which lies between STA and SolO. The GCS-fit locations are consistent with the in situ observations, where Wind detected FRw and STA and SolO intercepted FRe at opposite sides of the MC center.

In 2024 May, the scientific community observed intense solar eruptions that resulted in a great geomagnetic storm and auroral extensions, highlighting the need to document and quantify these events. This study mainly focuses on their quantification. The source active region (AR; NOAA Active Region 13664) evolved from 113 to 2761 millionths of the solar hemisphere between May 4 and 14. NOAA AR 13664’s magnetic free energy surpassed 10³³ erg on May 7, triggering 12 X-class flares on May 8–15. Multiple interplanetary coronal mass ejections (ICMEs) were produced from this AR, accelerating solar energetic particles toward Earth. According to satellite and interplanetary scintillation data, at least four ICMEs erupted from AR 13664, eventually overcoming and combining each other. The shock arrival at 17:05 UT on May 10 significantly compressed the magnetosphere down to ≈5.04 R _E and triggered a deep Forbush Decrease. GOES satellite data and ground-based neutron monitors confirmed a ground-level enhancement from 2 UT to 10 UT on 2024 May 11. The ICMEs induced exceptional geomagnetic storms, peaking at a provisional Dst index of −412 nT at 2 UT on May 11, marking the sixth-largest storm since 1957. The AE and AL indices showed great auroral extensions that located the AE/AL stations into the polar cap. We gathered auroral records at that time and reconstructed the equatorward boundary of the visual auroral oval to 29.°8 invariant latitude. We compared naked-eye and camera auroral visibility, providing critical caveats on their difference. We also confirmed global disturbances of the storm-enhanced density of the ionosphere.

During their propagation, coronal mass ejections (CMEs) and prominences sometimes display a nonradial motion. During the years after the solar minimum, the CME central position angle tended to be offset closer to the equator compared to that of the associated prominence eruptions (PE). No such effect was observed during solar maximum. The purpose of this paper is to investigate the latitudinal offsets of CMEs with respect to their source regions. We study 256 events from SC 24 and SC 25, listed in the Coordinate Data Analysis Workshop Data Center. We analyzed the CMES radial offset from the associated PEs by comparing their latitudes in the plane of the sky. This work is an extension of the previous work by Gopalswamy et al., but with an independent data set. We have confirmed the systematic equatorward offset of CME from the solar source region for the rising phase of Solar Cycle 25. Our analysis of the relation between CME linear speed and PE-CME latitudinal offset indicated that the velocities of the deflected CMEs are mainly in the range of 200 and 800 km s⁻¹. In this study, we compared the nonradial offsets for the rising and decay phases of SC 24 and our analysis has shown that during the decay phase more events deflected toward the pole can be observed. The observed variation is attributed to the presence of a substantial number of low-latitude coronal holes during the decay phase and to the influence from nearby active regions.

Coronal mass ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties. This is because CMEs interact with the ambient solar wind and other large-scale magnetic field structures. In this work, we report on the observations of the 2012 October 5 stealth CME using coronagraphic and heliospheric images. We find clear evidence of a continuous rotation of the CME, i.e., an increase in the tilt angle, estimated using the graduated cylindrical shell (GCS) reconstruction at different heliocentric distances, up to 58 R _⊙. We find a further increase in the tilt at L1 estimated from the toroidal and cylindrical flux rope fitting on the in situ observations of interplanetary magnetic field (IMF) and solar wind parameters. This study highlights the importance of observations of Heliospheric Imager (HI), on board the Solar Terrestrial Relations Observatory. In particular, the GCS reconstruction of CMEs in the HI field of view promises to bridge the gap between the near-Sun and in situ observations at the L1. The changes in the CME tilt have significant implications for the space weather impact of stealth CMEs.

Coronal mass ejections (CMEs) can generate the most severe geomagnetic disturbances. One of the most critical factors affecting a CME’s geoeffectiveness is its trajectory. It is crucial to determine whether and when CME will hit Earth. It is commonly assumed that CMEs experience a deflection of propagation in the corona and in interplanetary space. In this study, we analyze more than 14,000 CMEs listed in the Coordinate Data Analysis Workshop (CDAW) catalog during 1996–2022 to estimate their deflection in the Large and Spectrometric Coronagraph field of view (LFOV). In our statistical analysis, the deflection was determined using the CME height–time measurements listed in the CDAW catalog. We have shown that, in the solar corona, CME deflection is a common phenomenon, heavily influenced by solar activity cycles as well as phases of these cycles. We have demonstrated that during periods of solar activity minima the deflection of CMEs is mostly toward the equator, and during periods of maxima it is mostly toward the poles. This general trend of deflection is further modified by the specific structure of the magnetic field generated during successive cycles of solar activity (e.g., the asymmetry between the hemispheres). A systematic increase in deflection with time was also recognized. We have also found that the deflection increases linearly with the distance from the Sun in the LFOV (the line slope is 0.5).

The sustained gamma-ray emission (SGRE) from the Sun is a prolonged enhancement of >100 MeV gamma-ray emission that extends beyond the flare impulsive phase. The origin of the >300 MeV protons resulting in SGRE is debated, with both flares and shocks driven by coronal mass ejections (CMEs) being the suggested sites of proton acceleration. We compared the near-Sun acceleration and space speed of CMEs with “Prompt” and “Delayed” (SGRE) gamma-ray components. We found that “Delayed”-component-associated CMEs have higher initial accelerations and space speeds than “Prompt Only”-component-associated CMEs. We selected halo CMEs (HCMEs) associated with type II radio bursts (shock-driving HCMEs) and compared the average acceleration and space speed between HCME populations with or without SGRE events, major solar energetic particle (SEP) events, metric, or decameter-hectometric (DH) type II radio bursts. We found that the SGRE-producing HCMEs associated with a DH type II radio burst and/or a major SEP event have higher space speeds and especially initial accelerations than those without an SGRE event. We estimated the radial distances and speeds of the CME-driven shocks at the end time of the 2012 January 23 and March 7 SGRE events using white-light images of STEREO Heliospheric Imagers and radio dynamic spectra of Wind WAVES. The shocks were at the radial distances of 0.6–0.8 au and their speeds were high enough (≈975 km s⁻¹ and ≈750 km s⁻¹, respectively) for high-energy particle acceleration. Therefore, we conclude that our findings support the CME-driven shock as the source of >300 MeV protons.