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New Results on the Direct Observations of Thermal Radio Emission from a Solar Coronal Mass Ejection
Ramesh, R.; Kumari, A.; Kathiravan, C. +2 more
We report observations of thermal emission from the frontal structure of a coronal mass ejection (CME) using data obtained with the Gauribidanur RAdioheliograPH simultaneously at 80 and 53 MHz on May 1, 2016. The CME was due to activity on the far side of the Sun, but near its limb. No nonthermal radio burst activity was noticed. This provided an …
Flux Erosion of Magnetic Clouds by Reconnection With the Sun's Open Flux
Nandy, Dibyendu; Pal, Sanchita; Dash, Soumyaranjan
Magnetic clouds (MCs) are flux rope magnetic structures forming a subset of solar coronal mass ejections, which have significant space weather impacts. The geoeffectiveness of MCs depends on their properties, which evolve during their interplanetary passage. Based on an analysis of observations spanning two solar cycles, we establish that MCs inte…
Low-Frequency Radio Observations of the "Quiet" Corona During the Descending Phase of Sunspot Cycle 24
Ramesh, R.; Kumari, A.; Kathiravan, C. +3 more
We carried out a statistical study of the "quiet" solar corona during the descending phase of the Sunspot Cycle 24 (i.e., January 2015 to May 2019) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) at 53 and 80 MHz simultaneously. Our results show that the equatorial (east-west) diameters of the solar corona at the above two freque…
Global Distribution of the Solar Wind Flux and Velocity From SOHO/SWAN During SC-23 and SC-24
Schmidt, W.; Quémerais, E.; Koutroumpa, D. +1 more
We analyze SOHO (SOlar Heliospheric Observatory)/SWAN (Solar Wind ANisotropy) hydrogen Lyman-α data collected between 1996 and 2018 to derive the solar wind latitudinal distribution over time. Full-sky interplanetary Lyman-α maps are inverted to derive the total hydrogen ionization rate latitude profiles, normalized to proton charge-exchange and p…
Observations on a Series of Merging Magnetic Flux Ropes Within an Interplanetary Coronal Mass Ejection
Zhao, Yan; Feng, Hengqiang; Zhao, Guoqing +2 more
Coronal mass ejections (CMEs) are intense solar explosive eruptions. CMEs are highly important players in solar-terrestrial relationships, and they have important consequences for major geomagnetic storms and energetic particle events. It has been unclear how CMEs evolve when they propagate in the heliosphere. Here we report an interplanetary CME …
An Empirical Model of the Variation of the Solar Lyman-α Spectral Irradiance
Kretzschmar, Matthieu; Curdt, Werner; Snow, Martin
We propose a simple model that computes the spectral profile of the solar irradiance in the hydrogen Lyman alpha line, H Ly-α (121.567 nm), from 1947 to present. Such a model is relevant for the study of many astronomical environments, from planetary atmospheres to interplanetary medium. This empirical model is based on the SOlar Heliospheric Obse…
Methodology to create a new total solar irradiance record: Making a composite out of multiple data records
Schöll, Micha; Dudok de Wit, Thierry; Fröhlich, Claus +1 more
Many observational records critically rely on our ability to merge different (and not necessarily overlapping) observations into a single composite. We provide a novel and fully traceable approach for doing so, which relies on a multiscale maximum likelihood estimator. This approach overcomes the problem of data gaps in a natural way and uses data…
Quantitative prediction of type II solar radio emission from the Sun to 1 AU
Cairns, Iver H.; Schmidt, J. M.
Coronal mass ejections (CMEs) are frequently associated with shocks and type II solar radio bursts. Despite involving fundamental plasma physics and being the archetype for collective radio emission from shocks, type II bursts have resisted detailed explanation for over 60 years. Between 29 November and 1 December 2013 the two widely separated spa…
Near-Sun speed of CMEs and the magnetic nonpotentiality of their source active regions
Tiwari, Sanjiv K.; Winebarger, Amy R.; Venkatakrishnan, P. +3 more
We show that the speed of the fastest coronal mass ejections (CMEs) that an active region (AR) can produce can be predicted from a vector magnetogram of the AR. This is shown by logarithmic plots of CME speed (from the SOHO Large Angle and Spectrometric Coronagraph CME catalog) versus each of ten AR-integrated magnetic parameters (AR magnetic flux…
Anomalous expansion of coronal mass ejections during solar cycle 24 and its space weather implications
Gopalswamy, Nat; Akiyama, Sachiko; Yashiro, Seiji +3 more
The familiar correlation between the speed and angular width of coronal mass ejections (CMEs) is also found in solar cycle 24, but the regression line has a larger slope: for a given CME speed, cycle 24 CMEs are significantly wider than those in cycle 23. The slope change indicates a significant change in the physical state of the heliosphere, due…