First solar electron events observed by EPD aboard Solar Orbiter

2021 ◽  
Author(s):  
Raúl Gómez-Herrero ◽  
Daniel Pacheco ◽  
Alexander Kollhoff ◽  
Francisco Espinosa Lara ◽  
Johan L. Freiherr von Forstner ◽  
...  
Keyword(s):  
Heavy Ions ◽  
Extreme Ultraviolet ◽  
Transport Processes ◽  
Relativistic Electrons ◽  
Radio Bursts ◽  
Solar Origin ◽  
Time Profiles ◽  
Field Environment ◽  
Multiple Spacecraft ◽  
Excellent Energy Resolution

<p>The first solar electron events detected by Solar Orbiter were observed by the Energetic Particle Detector (EPD) suite during July 11-23, 2020, when the spacecraft was at heliocentric distances between 0.61 and 0.69 au. We combined EPD electron observations from 4 keV to the relativistic range (few MeV), radio dynamic spectra and extreme ultraviolet (EUV) observations from multiple spacecraft in order to identify the solar origin of these electron events. Electron anisotropies and timing as well as the plasma and magnetic field environment were evaluated to characterize the interplanetary transport conditions. We found that all the electron events were clearly associated with type III radio bursts. EUV jets were also found in association with all of them except one. A diversity of time profiles and pitch-angle distributions (ranging from almost isotropic to beam-like) was observed. These observations indicate that different source locations and different magnetic connectivity and transport conditions were likely involved. The broad spectral range covered by EPD with excellent energy resolution and the high time cadence ensure that future observations close to the Sun will contribute to the understanding of the acceleration, release, and transport processes of energetic particles. EPD observations will play a key role in the identification of the sources of impulsive events and the links between the near-relativistic electrons and the ion populations enriched in <sup>3</sup>He and heavy ions</p><p> </p>

scholarly journals Variable emission mechanism of a Type IV radio burst

2019 ◽  
Vol 623 ◽  
pp. A63 ◽  
Author(s):  
D. E. Morosan ◽  
E. K. J. Kilpua ◽  
E. P. Carley ◽  
C. Monstein
Keyword(s):  
Frequency Band ◽  
Radio Burst ◽  
Extreme Ultraviolet ◽  
Imaging Spectroscopy ◽  
Continuum Emission ◽  
Particle Accelerators ◽  
Radio Bursts ◽  
Emission Mechanism ◽  
Type Iv ◽  
Dynamic Spectra

Context. The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011. Methods. We used radio imaging from the Nançay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA’s Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electron-cyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra.

scholarly journals Evolution of the dispersionless injection boundary associated with substorms

2005 ◽  
Vol 23 (3) ◽  
pp. 877-884 ◽  
Author(s):  
T. Sarris ◽  
X. Li
Keyword(s):  
Leading Edge ◽  
Transport Processes ◽  
Pulse Field ◽  
Magnetospheric Substorms ◽  
Narrow Region ◽  
The Earth ◽  
Electric And Magnetic Fields ◽  
Sudden Appearance ◽  
Injection Region ◽  
Multiple Spacecraft

Abstract. One manifestation of energetic particle acceleration during magnetospheric substorms is the sudden appearance of particle injections into the inner magnetosphere, often observed near geosynchronous orbit. Injections that show simultaneous flux increases in all energy ranges of a detector are called dispersionless injections, and are most often observed in a narrow region around local midnight. In these events it is assumed that the satellite is located close to or inside the region where acceleration and/or transport processes are taking place, called the injection region. We present a study of the location, extent and temporal evolution of the injection region, based on simulation results of a model of the expansion of the electric and magnetic fields associated with a substorm. The model simulates the fields during a substorm onset with an electric field and consistent magnetic field pulse that propagates towards the Earth with a decreasing speed. Our simulation shows that the dispersionless injection boundary can be considered coincident with the leading edge of the pulse field, which transports particles toward the Earth across a certain range of local time. Under the same model field, the dispersionless injection boundary shifts eastward for electrons and westward for protons, consistent with the observation results deduced from statistical analysis of multiple spacecraft measurements.

scholarly journals Role of eddy diffusion in the delayed ionospheric response to solar flux changes

2021 ◽  
Vol 39 (4) ◽  
pp. 641-655
Author(s):  
Rajesh Vaishnav ◽  
Christoph Jacobi ◽  
Jens Berdermann ◽  
Mihail Codrescu ◽  
Erik Schmölter
Keyword(s):  
Solar Activity ◽  
Extreme Ultraviolet ◽  
Solar Rotation ◽  
Eddy Diffusion ◽  
Transport Processes ◽  
Solar Flux ◽  
Ionospheric Delay ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Response

Abstract. Simulations of the ionospheric response to solar flux changes driven by the 27 d solar rotation have been performed using the global 3-D Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) physics-based numerical model. Using the F10.7 index as a proxy for solar extreme ultraviolet (EUV) variations in the model, the ionospheric delay at the solar rotation period is well reproduced and amounts to about 1 d, which is consistent with satellite and in situ measurements. From mechanistic CTIPe studies with reduced and increased eddy diffusion, we conclude that the eddy diffusion is an important factor that influences the delay of the ionospheric total electron content (TEC). We observed that the peak response time of the atomic oxygen to molecular nitrogen ratio to the solar EUV flux changes quickly during the increased eddy diffusion compared with weaker eddy diffusion. These results suggest that an increase in the eddy diffusion leads to faster transport processes and an increased loss rate, resulting in a decrease in the ionospheric time delay. Furthermore, we found that an increase in solar activity leads to an enhanced ionospheric delay. At low latitudes, the influence of solar activity is stronger because EUV radiation drives ionization processes that lead to compositional changes. Therefore, the combined effect of eddy diffusion and solar activity leads to a longer delay in the low-latitude and midlatitude region.

A Discussion on solar studies with special reference to space observations - Extreme ultraviolet emission during flares

1971 ◽  
Vol 270 (1202) ◽  
pp. 117-125 ◽  
Keyword(s):  
Extreme Ultraviolet ◽  
Suitable Model ◽  
X Rays ◽  
Radio Waves ◽  
Ultraviolet Emission ◽  
Magnetic Instability ◽  
X Ray ◽  
Time Profiles ◽  
Peak Flux ◽  
Cool Plasma

A number of time profiles are presented which show how the flux of radiation in the wavelength bands 0.1 to 0.3 nm, 0.3 to 0.9 nm, 0.8 to 1.6 nm and at 30.4 nm change during flares. The first sign of a flare is often a decrease of flux at 30.4 nm followed by an increase in the X-ray emission. In general, the higher the photon energy, the earlier the peak flux is reached, although any increase observed at 30.4 nm seems to peak before the X -ray flux. It is concluded that a model in which a mass of gas in the upper chromosphere is heated by shock waves or incident energetic particles does not explain the observations. What appears to be a more suitable model is suggested. Cool plasma from low in the chromosphere passes through a region of magnetic instability and is heated during the passage. In this way the material of the X -ray emitting region is heated to a high tem perature a little at a time. The intensity of X-rays observed in each waveband is proportional to the volume of gas produced up to that time at the corresponding tem perature. As the instability decays the gas passing through it can no longer be heated to the temperatures reached earlier and the emission of longer wavelength X-rays becomes dominant. The emission of y -rays and radio waves can also be explained

Accurate wavelengths of resonance lines in Zn-like heavy ions

2003 ◽  
Vol 81 (7) ◽  
pp. 911-918 ◽  
Author(s):  
S B Utter ◽  
P Beiersdorfer ◽  
E Träbert
Keyword(s):  
Electron Beam ◽  
Heavy Ions ◽  
Ion Trap ◽  
Extreme Ultraviolet ◽  
Electron Beam Ion Trap ◽  
Flat Field ◽  
Improved Accuracy

Using an electron-beam ion trap and a flat-field spectrometer, the extreme ultraviolet resonance lines of Zn-like ions of Yb, W, Au, Pb, Th, and U were observed and their wavelengths measured with greatly improved accuracy. The results are compared to those from laser-produced plasmas and to theory, and significant differences are found. PACS Nos.: 32.30.Jc, 39.30.+w

scholarly journals Extreme ultraviolet and visible spectroscopy of promethiumlike heavy ions

2015 ◽  
Vol 92 (2) ◽  
Author(s):  
Yusuke Kobayashi ◽  
Kai Kubota ◽  
Kazuki Omote ◽  
Akihiro Komatsu ◽  
Junpei Sakoda ◽  
...  
Keyword(s):  
Heavy Ions ◽  
Extreme Ultraviolet ◽  
Visible Spectroscopy

scholarly journals Thermal and Nonthermal Interpretations of Flare X-Ray Bursts

1975 ◽  
Vol 68 ◽  
pp. 211-231
Author(s):  
S. Kahler
Keyword(s):  
Radio Bursts ◽  
Polarization Data ◽  
Gradual Rise ◽  
X Ray ◽  
Temporal Parameters ◽  
Time Profiles ◽  
Special Events

Various authors have presented arguments for either the thermal or the nonthermal interpretations of impulsive E > 20 KeV X-ray bursts and slowly varying E < 10 keV X-ray bursts. In this review the arguments for and against the prevailing opinion that the impulsive bursts are nonthermal and the slowly varying bursts are thermal are presented.For the impulsive bursts we discuss the spectra, electron mean free paths, center-to-limb distributions of both the numbers of events and spectra of events, and polarization data as relevant criteria. For the slowly varying events we discuss electron self collision times, distribution of X-ray temporal parameters, associated gradual rise and fall radio bursts, spectral and time profiles of special events and center-to-limb distributions of numbers of events as the relevant criteria.

scholarly journals A study on the relationship of type III radio bursts CME and solar flares during the active period October-November 2003

2008 ◽  
Vol 4 (S257) ◽  
pp. 361-363
Author(s):  
Michaella Thanassa ◽  
Eleftheria Mitsakou ◽  
Panagiota Preka-Papadema ◽  
Xenophon Moussas ◽  
Panagiotis Tsitsipis ◽  
...  
Keyword(s):  
Solar Flares ◽  
Relativistic Electrons ◽  
Active Period ◽  
Radio Bursts ◽  
Characteristic Type ◽  
Type Iii ◽  
Intense Activity ◽  
Relationship Of ◽  
The Relationship

AbstractWithin a period of intense activity (20 October to 5 November 2003), the injection and propagation of near relativistic electrons, resulted in hundreds of type III bursts recorded by the ARTEMISIV radio spectrograph (20–650 MHz). For a number of these type III events association with GOES SXR/Hα flare and/or SOHO/LASCO CME was established. We study the variation of characteristic type III parameters and their relationship with features of the associated flares and/or CMEs.

scholarly journals Mergers and Non-Thermal Processes in Clusters

2005 ◽  
Vol 13 ◽  
pp. 291-295 ◽  
Author(s):  
Craig L. Sarazin
Keyword(s):  
Gamma Ray ◽  
Extreme Ultraviolet ◽  
Cosmological Parameters ◽  
Thermal Processes ◽  
Relativistic Electrons ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Cold Fronts ◽  
Electrons And Ions ◽  
Large Populations

AbstractClusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Mergers drive shocks in the intra-cluster gas which heat the intra-cluster gas. Mergers disrupt cluster cooling cores. Mergers produce large, temporary increases in the X-ray luminosities and temperatures of cluster; such merger boost may bias estimates of cosmological parameters from clusters. Chandra observations of the X-ray signatures of mergers, particularly “cold fronts,” will be discussed. X-ray observations of shocks can be used to determine the kinematics of the merger. As a result of particle acceleration in shocks and turbulent acceleration following mergers, clusters of galaxies should contain very large populations of relativistic electrons and ions. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from non-thermal particles accelerated in these shocks are described.

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