Context.
Corotating interaction regions (CIRs), formed by the interaction of slow solar wind and fast streams that originate from coronal holes (CHs), produce recurrent Forbush decreases, which are ...short-term depressions in the galactic cosmic ray (GCR) flux.
Aims.
Our aim is to prepare a reliable set of CIR measurements to be used as a textbook for modeling efforts. For that purpose, we observe and analyse a long-lived CIR, originating from a single CH, recurring in 27 consecutive Carrington rotations 2057–2083 in the time period from June 2007–May 2009.
Methods.
We studied the in situ measurements of this long-lived CIR as well as the corresponding depression in the cosmic ray (CR) count observed by SOHO/EPHIN throughout different rotations. We performed a statistical analysis, as well as the superposed epoch analysis, using relative values of the key parameters: the total magnetic field strength,
B
, the magnetic field fluctuations,
dBrms
, plasma flow speed,
v
, plasma density,
n
, plasma temperature,
T
, and the SOHO/EPHIN F-detector particle count, and CR count.
Results.
We find that the mirrored CR count-time profile is correlated with that of the flow speed, ranging from moderate to strong correlation, depending on the rotation. In addition, we find that the CR count dip amplitude is correlated to the peak in the magnetic field and flow speed of the CIR. These results are in agreement with previous statistical studies. Finally, using the superposed epoch analysis, we obtain a generic CIR example, which reflects the in situ properties of a typical CIR well.
Conclusions.
Our results are better explained based on the combined convection-diffusion approach of the CIR-related GCR modulation. Furthermore, qualitatively, our results do not differ from those based on different CHs samples. This indicates that the change of the physical properties of the recurring CIR from one rotation to another is not qualitatively different from the change of the physical properties of CIRs originating from different CHs. Finally, the obtained generic CIR example, analyzed on the basis of superposed epoch analysis, can be used as a reference for testing future models.
Aims.
The first relativistic solar proton event of solar cycle 25 was detected on 28 October 2021 by neutron monitors (NMs) on the ground and particle detectors on board spacecraft in near-Earth ...space. This is the first ground-level enhancement (GLE) of the current cycle. A detailed reconstruction of the NM response together with the identification of the solar eruption that generated these particles is investigated based on in situ and remote-sensing measurements.
Methods.
In situ proton observations from a few MeV to ∼500 MeV were combined with the detection of a solar flare in soft X-rays, a coronal mass ejection, radio bursts, and extreme ultraviolet (EUV) observations to identify the solar origin of the GLE. Timing analysis was performed, and a relation to the solar sources was outlined.
Results.
GLE73 reached a maximum particle rigidity of ∼2.4 GV and is associated with type III, type II, and type IV radio bursts and an EUV wave. A diversity of time profiles recorded by NMs was observed. This points to the event having an anisotropic nature. The peak flux at
E
> 10 MeV was only ∼30 pfu and remained at this level for several days. The release time of ≥1 GV particles was found to be ∼15:40 UT. GLE73 had a moderately hard rigidity spectrum at very high energies (
γ
∼ 5.5). Comparison of GLE73 to previous GLEs with similar solar drivers is performed.
The solar modulation of galactic cosmic rays (GCR) can be studied in detail by examining long-term variations of the GCR energy spectrum (
e.g.
on the scales of a solar cycle). With almost 20 years ...of data, the
Electron Proton Helium INstrument
(EPHIN) onboard the
SOlar and Heliospheric Observatory
(SOHO) is well suited for this kind of investigation. Although the design of the instrument is optimised to measure proton and helium isotope spectra up to
50
MeV
nucleon
−
1
, the capability exists to determine proton energy spectra from 250 MeV up to above 1.6 GeV. Therefore we developed a sophisticated inversion method to calculate such proton spectra. The method relies on a GEANT4 Monte Carlo simulation of the instrument and a simplified spacecraft model that calculates the energy-response function of EPHIN for electrons, protons, and heavier ions. For validation purposes, proton spectra based on this method are compared to various balloon missions and space instrumentation. As a result we present annual galactic cosmic-ray spectra from 1995 to 2014.
Solar energetic particle events and galactic cosmic rays are important aspects of space weather. Investigating them requires consistent measurements of electrons and ions over long time periods, that ...is, over more than a solar cycle. The Electron Proton Helium INstrument onboard the SOlar and Heliospheric Observatory is operational since 1995 and was designed to measure electrons in the energy range of 0.3 to 10 MeV as well as protons and helium ions in the energy range from 4 to 50 MeV per nucleon in four different coincidence channels with 1‐min resolution. Early in the mission and in 2017 two of six detectors became noisy and had to be switched of reducing the number of coincidence channels from 4 to 2, and thereby significantly reducing the energy resolution of the instrument. In order to restore the original count rate channels we present here a new data analysis applying the so called dE/dx − dE/dx method. A data set with different temporal resolutions from 1 min to a day has been generated for the whole ongoing SOlar and Heliospheric Observatory mission from 1995 to 2018. The resulting data sets are successfully validated against measurements from instruments close to Earth. Studies with regard to long‐term variation of the measured flux with special emphasis on the contribution of individual solar energetic particle events to the fluence observed over more than two solar cycles are presented here.
Key Points
A new data product of SOHO/EPHIN with consistent data quality over more than two solar cycles is provided
The fluence of protons and helium particles in the energy range from 5 to 50 MeV per nucleon is dominated by individual SEP events
Abstract
In this paper we explore the idea of using multi-spacecraft observations of Jovian electrons to measure the 3D distribution of these particles in the inner heliosphere. We present ...simulations of Jovian electron intensities along selected spacecraft trajectories for 2021 and compare these, admittedly qualitatively, to these measurements. Using the data–model comparison we emphasize how such a study can be used to constrain the transport parameters in the inner heliosphere, and how this can lead to additional insight into energetic particle transport. Model results are also shown along the expected trajectories of selected spacecraft, including the off-ecliptic phase of the Solar Orbiter mission from 2025 onward. Lastly, we revisit the use of historical data and discuss upcoming missions that may contribute to Jovian electron measurements.
The Sun is an effective particle accelerator that produces solar energetic particle (SEP) events, during which particles of up to several GeVs can be observed. These events, when they are observed at ...Earth with the neutron monitor network, are called ground-level enhancements (GLEs). Although these events with their high-energy component have been investigated for several decades, a clear relation between the spectral shape of the SEPs outside the Earth’s magnetosphere and the increase in neutron monitor count rate has yet to be established. Hence, an analysis of these events is of interest for the space weather and for the solar event community.
In this article, SEP events with protons accelerated to above 500 MeV were identified using data obtained with the
Electron Proton Helium Instrument
(EPHIN) onboard the
Solar and Heliospheric Observatory
(SOHO) between 1995 and 2015. For a statistical analysis, onset times were determined for the events and the proton energy spectra were derived and fitted with a power law.
As a result, we present a list of 42 SEP events with protons accelerated to above 500 MeV measured with the EPHIN instrument onboard SOHO. The statistical analysis based on the fitted spectral slopes and absolute intensities is discussed, with special emphasis on whether an event has been observed as a GLE. Furthermore, we are able to determine that the derived intensity at 500 MeV and the observed increase in neutron monitor count rate are correlated for a subset of events.
The aim of this study was to examine if contrast-enhanced multislice spiral computed tomography (MSCT) is comparable to contrast-enhanced magnetic resonance imaging (MRI) for depiction of acute ...myocardial infarction (MI).
Delayed-enhancement MRI of MI is well established, but there are no clinical reports about MSCT for this indication. Early perfusion deficit on MSCT has been reported to correlate with the presence of MI.
A total of 28 consecutive patients (23 men; 55.9 ± 11.4 years) with reperfused MI underwent contrast-enhanced cardiac 16-slice MSCT. Images were acquired in the arterial phase and the late phase 15 min after administration of 120 ml contrast material. Within 5 days, patients underwent MRI after administration of 0.2 mmol Gd-dimeglumine/kg/bodyweight. All examinations were completed within two weeks after MI. The area of MI was compared between the different imaging techniques using Bland-Altman method and multivariate analysis. Agreement of the contrast enhancement patterns was evaluated with a weighted kappa test.
Mean infarct size on MRI was 31.2 ± 22.5% per slice compared with 33.3 ± 23.8% per slice for late-enhancement MSCT and 24.5 ± 18.3% per slice for early-perfusion-deficit MSCT. Bland-Altman data showed a good agreement between late-enhancement MRI and late-enhancement MSCT. Contrast enhancement patterns demonstrated an excellent agreement between late-enhancement MRI and late-enhancement MSCT (kappa = 0.878). The results were worse comparing MRI and early-phase MSCT (kappa = 0.635).
Multislice spiral computed tomography allows for the assessment of acute MI. Late-enhancement MSCT appears to be as reliable as delayed contrast-enhanced MRI in assessing infarct size and myocardial viability in acute MI.
Context . The solar energetic particle analysis platform for the inner heliosphere (SERPENTINE) project, funded through the H2020-SPACE-2020 call of the European Union’s Horizon 2020 framework ...program, employs measurements of the new inner heliospheric spacecraft fleet to address several outstanding questions on the origin of solar energetic particle (SEP) events. The data products of SERPENTINE include event catalogs, which are provided to the scientific community. Aims . In this paper, we present SERPENTINE’s new multi-spacecraft SEP event catalog for events observed in solar cycle 25. Observations from five different viewpoints are utilized, provided by Solar Orbiter, Parker Solar Probe, STEREO A, Bepi Colombo, and the near-Earth spacecraft Wind and SOHO. The catalog contains key SEP parameters for 25–40 MeV protons, ~1 MeV electrons, and ~100 keV electrons. Furthermore, basic parameters of associated flares and type II radio bursts are listed, as are the coordinates of the observer and solar source locations. Methods . An event is included in the catalog if at least two spacecraft detect a significant proton event with energies of 25–40 MeV. The SEP onset times were determined using the Poisson-CUSUM method. The SEP peak times and intensities refer to the global intensity maximum. If different viewing directions are available, we used the one with the earliest onset for the onset determination and the one with the highest peak intensity for the peak identification. We furthermore aimed to use a high time resolution to provide the most accurate event times. Therefore, we opted to use a 1-min time resolution, and more time averaging of the SEP intensity data was only applied if necessary to determine clean event onsets and peaks. Associated flares were identified using observations from near Earth and Solar Orbiter. Associated type II radio bursts were determined from ground-based observations in the metric frequency range and from spacecraft observations in the decametric range. Results . The current version of the catalog contains 45 multi-spacecraft events observed in the period from November 2020 until May 2023, of which 13 events were found to be widespread (observed at longitudes separated by at least 80° from the associated flare location) and four could be classified as narrow-spread events (not observed at longitudes separated by at least 80° from the associated flare location). Using X-ray observations by GOES/XRS and Solar Orbiter/STIX, we were able to identify the associated flare in all but four events. Using ground-based and space-borne radio observations, we found an associated type II radio burst for 40 events. In total, the catalog contains 142 single event observations, of which 20 (45) have been observed at radial distances below 0.6 AU (0.8 AU). It is anticipated that the catalog will be extended in the future.
Context.
Solar Orbiter strives to unveil how the Sun controls and shapes the heliosphere and fills it with energetic particle radiation. To this end, its Energetic Particle Detector (EPD) has now ...been in operation, providing excellent data, for just over a year.
Aims.
EPD measures suprathermal and energetic particles in the energy range from a few keV up to (near-) relativistic energies (few MeV for electrons and about 500 MeV nuc
−1
for ions). We present an overview of the initial results from the first year of operations and we provide a first assessment of issues and limitations. In addition, we present areas where EPD excels and provides opportunities for significant scientific progress in understanding how our Sun shapes the heliosphere.
Methods.
We used the solar particle events observed by Solar Orbiter on 21 July and between 10 and 11 December 2020 to discuss the capabilities, along with updates and open issues related to EPD on Solar Orbiter. We also give some words of caution and caveats related to the use of EPD-derived data.
Results.
During this first year of operations of the Solar Orbiter mission, EPD has recorded several particle events at distances between 0.5 and 1 au from the Sun. We present dynamic and time-averaged energy spectra for ions that were measured with a combination of all four EPD sensors, namely: the SupraThermal Electron and Proton sensor (STEP), the Electron Proton Telescope (EPT), the Suprathermal Ion Spectrograph (SIS), and the High-Energy Telescope (HET) as well as the associated energy spectra for electrons measured with STEP and EPT. We illustrate the capabilities of the EPD suite using the 10 and 11 December 2020 solar particle event. This event showed an enrichment of heavy ions as well as
3
He, for which we also present dynamic spectra measured with SIS. The high anisotropy of electrons at the onset of the event and its temporal evolution is also shown using data from these sensors. We discuss the ongoing in-flight calibration and a few open instrumental issues using data from the 21 July and the 10 and 11 December 2020 events and give guidelines and examples for the usage of the EPD data. We explain how spacecraft operations may affect EPD data and we present a list of such time periods in the appendix. A list of the most significant particle enhancements as observed by EPT during this first year is also provided.
Aims. We studied the first multi-spacecraft high-energy solar energetic particle (SEP) event of solar cycle 25, which triggered a ground level enhancement on 28 October 2021, using data from multiple ...observers (Parker Solar Probe, STEREO-A, Solar Orbiter, GOES, SOHO, BepiColombo, and the Mars Science Laboratory) that were widely distributed throughout the heliosphere and located at heliocentric distances ranging from 0.60 to 1.60 AU. Methods. We present SEP observations at a broad energy range spanning from ∼10 to 600 MeV obtained from the different instruments. We performed detail modelling of the shock wave and we derived the 3D distribution and temporal evolution of the shock parameters. We further investigated the magnetic connectivity of each observer to the solar surface and examined the shock’s magnetic connection. We performed velocity dispersion analysis and time-shifting analysis to infer the SEP release time. We derived and present the peak proton flux spectra for all the above spacecraft and fluence spectra for major species recorded on board Solar Orbiter from the Suprathermal Ion Spectrograph (SIS). We performed 3D SEP propagation simulations to investigate the role of particle transport in the distribution of SEPs to distant magnetically connected observers. Results. Observations and modelling show that a strong shock wave formed promptly in the low corona. At the SEP release time windows, we find a connection with the shock for all the observers. PSP, STEREO-A, and Solar Orbiter were connected to strong shock regions with high Mach numbers (>4), whereas the Earth and other observers were connected to lower Mach numbers. The SEP spectral properties near Earth demonstrate two power laws, with a harder (softer) spectrum in the low-energy (high-energy) range. Composition observations from SIS (and near-Earth instruments) show no serious enhancement of flare-accelerated material. Conclusions. A possible scenario consistent with the observations and our analysis indicates that high-energy SEPs at PSP, STEREO-A, and Solar Orbiter were dominated by particle acceleration and injection by the shock, whereas high-energy SEPs that reached near-Earth space were associated with a weaker shock; it is likely that efficient transport of particles from a wide injection source contributed to the observed high-energy SEPs. Our study cannot exclude a contribution from a flare-related process; however, composition observations show no evidence of an impulsive composition of suprathermals during the event, suggestive of a non-dominant flare-related process.
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