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  • Sun  (2)
  • Astronomy  (1)
  • Corotating high-speed streams  (1)
  • SPACE SCIENCES (GENERAL)  (1)
  • 1
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    Bright Points and Subflares in Ultraviolet Lines and X-Rays (1999)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: We have analyzed an active region which was observed in H.alpha (Multichannel Subtractive Double Pass Spectrograph), in UV lines (SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X-rays. Using an extrapolation based on the Fourier transform, we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find two different zones: (1) a high-shear region (〉 70 deg) where subflares occur, and (2) a low-shear region along the magnetic inversion line where UV bright points are observed. In these latter regions the magnetic topology is complex with a mixture of polarities. According to the velocity field observed in the Si IV lamda.1402 line and the extrapolation of the magnetic field, we notice that each UV bright point is consistent with emission from low-rising loops with downflows at both ends. We notice some hard X-ray emissions above the bright-point regions with temperatures up to 8 x 10(exp 6) K, which suggests some induced reconnection due to continuous emergence of new flux. This reconnection is also enhanced by neighboring subflares.
    Keywords: Astronomy
    Type: Astrophysical Journal; Volume 510; 474-484
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Corotating particle enhancements out of the ecliptic plane (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: We have studied greater than 40 keV ion and electron enhancements seen at Ulysses from a series of corotating interaction regions (CIR), from mid-1992 until the end of 1993. The event intensity increased up to latitude 20 deg S; after that the ion flux maxima decreased by approximately 23%/deg while the electron maxima decreased more erratically, and more slowly, during the last half of 1993. After April, 1993, the electron increases lagged the ions by up to four days. The electron energy spectrum hardened both towards the end of the events and as the latitude went above approximately 35 deg. The electron/ion delays and the electron spectral hardening are related to the three-dimensional structure of the reverse shocks at high latitudes. The H/He ratio at approximately 0.4-1.2 MeV/nucleon decreased towards the end of each event; the mean minimum value was 3.5 +/- 0.3, lower than observed in earlier studies of CIR-associated events near the ecliptic plane. The He increases have recurred with a period of 26.0 days. There have been two phase changes: +4.3 days (February 1993) and +2.4 days (August 1993), related to changes in the coronal structure of the source regions for the high speed solar wind streams.
    Keywords: SPACE SCIENCES (GENERAL)
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 14; p. 1561-1564
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
    Electronic Resource
    Electronic Resource
    The Large Angle Spectroscopic Coronagraph (LASCO) (1995)
    Springer
    Solar physics 162 (1995), S. 357-402 
    Details
    ISSN: 1573-093X
    Keywords: Sun ; Corona ; Coronagraph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Large Angle Spectroscopic Coronagraph (LASCO) is a three coronagraph package which has been jointly developed for the Solar and Heliospheric Observatory (SOHO) mission by the Naval Research Laboratory (USA), the Laboratoire d'Astronomie Spatiale (France), the Max-Planck-Institut für Aeronomie (Germany), and the University of Birmingham (UK). LASCO comprises three coronagraphs, C1, C2, and C3, that together image the solar corona from 1.1 to 30 R⊙ (C1: 1.1 – 3 R⊙, C2: 1.5 – 6 R⊙, and C3: 3.7 – 30 R⊙). The C1 coronagraph is a newly developed mirror version of the classic internally-occulted Lyot coronagraph, while the C2 and C3 coronagraphs are externally occulted instruments. High-resolution imaging spectroscopy of the corona from 1.1 to 3 R⊙ can be performed with the Fabry-Perot interferometer in C1. High-volume memories and a high-speed microprocessor enable extensive on-board image processing. Image compression by a factor of about 10 will result in the transmission of 10 full images per hour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00733434
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    IMF connection for energetic protons observed at Ulysses via mid-latitude solar wind rarefaction regions (1995)
    Springer
    Space science reviews 72 (1995), S. 309-314 
    Details
    ISSN: 1572-9672
    Keywords: Heliosphere ; Energetic particles ; Corotating high-speed streams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As Ulysses moved inward and southward from mid-1992 to early 1994 we noticed the occasional occurrence of “inter-events”, lasting about 10 days and falling between the recurrent events, observed at proton energies of 0.48–97 MeV, associated with Corotating Interaction Regions (CIR). These inter-events were present for several sequences of two or more solar rotations at intensity levels around 1% of those of the neighbouring main events. When we compared the Ulysses events with those measured on IMP-8 at 1 AU we saw that the inter-events appeared at Ulysses after the extended emission (〉10 days) of large fluxes of solar protons of the same energy that lasted at least one solar rotation at 1 AU. The inter-events fell completely within the rarefaction regions (dv/dt〈0) of the recurrent solar wind streams. The interplanetary magnetic field (IMF) lines in the rarefactions map back to the narrow range of longitudes at the Sun which mark the eastern edge of the source region of the high speed stream. Thus the inter-events are propagating at mid-latitudes to Ulysses along field lines free from stream-stream interactions. They are seen in the 0.39–1.28 MeV/nucleon He, which exhibit a faster decay, but almost never in the 38–53 keV electrons. We show that the inter-events are unlikely to be accelerated by reverse shocks associated with the CIRs and that they are more likely to be accelerated by sequences of solar events and transported along the IMF in the rarefactions of the solar wind streams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768796
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Energy input for explosive events in the transition zone (1994)
    Springer
    Space science reviews 70 (1994), S. 69-75 
    Details
    ISSN: 1572-9672
    Keywords: Sun ; Transition zone ; Explosive events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is suggested that the energy input for explosive events in the transition zone comes from precipitating ions, typically of energies of a few×102 keV/nucleon, accelerated in the high corona. The energetics of the process are discussed, together with implications for coronal heating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777844
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    Paper (German National Licenses)
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