The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs

Abstract

[1] A corotating interaction region (CIR) is formed when fast coronal hole origin solar wind overtakes slow solar wind and forms a region of compressed plasma and magnetic field. The slow wind upstream of the coronal hole fast wind can be either of helmet streamer origin or pseudostreamer origin. For a collection of 125 CIR-driven geomagnetic storms, the slow wind ahead of each CIR is examined; for those storm not containing ejecta, each CIR is categorized as a helmet streamer CIR (74 of the 125 storms) or a pseudostreamer CIR (11 of the 125 storms). Separate superposed epoch studies are performed on the two groups to discern the differences between storms driven by pseudostreamer CIRs and those driven by helmet streamer CIRs. A major difference is that pseudostreamer CIR storms tend not to have a calm before the storm, so the outer plasmasphere does not refill before storm onset, and the outer electron radiation belt does not exhibit a pre-storm decay. The superdense plasma sheet is weaker for pseudostreamer CIR storms, and the dropout of the electron radiation belt is weaker. Pseudostreamer CIR storms and helmet streamer CIR storms tend to be of the same strength as measured by the magnitude of Kp, MBI (midnight boundary index), or Dst.Citation: Borovsky, J. E., and M. H. Denton (2013), The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs,

The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

“…To discern this timing, the properties of pertinent solar wind parameters will be examined with respect to the dropouts and recoveries. The pertinent solar wind measurements that are available in the CPA era are the solar wind speed v sw (for determining the timing of the slow‐to‐fast wind transition across the CIR), the solar wind flow longitude φ sw (for determining the timing of the east‐west flow deflection in the CIR), the solar wind magnetic field strength B mag (for determining the extent of the CIR compression and the location of the peak compression [ Borovsky and Denton , , ]), the solar wind density n sw (for determining the importance of ram pressure), and the proton specific entropy S p = T sw / n sw 2/3 (for determining the transition from low‐entropy streamer belt plasma to high‐entropy coronal hole origin plasma [cf. Intrilligator and Siscoe , ; Borovsky and Denton , ]).…”

“…Table ). In the modern era with the availability of quality solar wind measurements, the authors have identified high‐speed stream‐driven storms by [e.g., Denton and Borovsky , ; Borovsky and Denton , , ] (1) identifying corotating interaction regions (CIRs) in the solar wind data, (2) looking for long‐lived high‐speed streams in the solar wind data that follow the CIRs, and (3) looking at the Kp index to ensure that a storm occurred. Then (4) the magnetic field, proton temperature, and electron strahl structure of the solar wind data are examined to ensure that the CIR is not dominated by a magnetic cloud.…”

Short-term variability of the Sun-Earth system: an overview of progress made during the CAWSES-II period

“…Polar coronal holes indicate the strength of the polar field and hence the level of solar activity in the following cycle (Gopalswamy et al 2012a;Selhorst et al 2011;Shibasaki 2013;Mordvinov and Yazev 2014;Altrock 2014). Coronal holes in the equatorial region are good indicators of imminent high-speed streams (HSS) and CIRs arriving at Earth (Tsurutani et al 1995(Tsurutani et al , 2006Cranmer 2009;Verbanac et al 2011;Akiyama et al 2013;Borovsky and Denton 2013). The empirical relationships established between HSS characteristics and the related geomagnetic activity provides an advance warning of impending CIR storms (Tsurutani et al 2006;Verbanac et al 2011).…”

“…Keesee et al (2014) performed superposed epoch analysis of 21 CME-driven and 15 CIR-driven storms during the June 2008 to April 2012 time frame and different evolutions of the ion temperature: the ion temperature increased in the recovery phase of CIR storms, while it increased rapidly at the onset of CME storms and cooled off during the main phase. Borovsky and Denton (2013) compared CIR storms associated with helmet streamers and pseudo-streamers. They found that pseudo-streamer CIR storms tend not to have a calm (Tsurutani et al 1995) before the storm, with weaker superdense plasma sheet and electron radiation belt dropout.…”

Lifecycle of a Large-Scale Polar Coronal Pseudostreamer/Cavity System

“…To date, pseudostreamer research mainly focused on their magnetic configurations and their role in both solar wind and space weather, while their thermal and density properties are poorly known. Borovsky and Denton (2013) showed that magnetic storms driven by pseudostreamers have systematically different phenomenologies than those driven from streamers. Zhao et al (2013) proposed that pseudostreamers are associated with extreme-proton-flux slow solar wind measured by the Ulysses mission.…”