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  • 1
    Electronic Resource
    Electronic Resource
    Simultaneous interplanetary scintillation and optical measurements of the acceleration of the slow solar wind (2000)
    Springer
    Annales geophysicae 18 (2000), S. 995-1002 
    Details
    ISSN: 0992-7689
    Keywords: Interplanetary physics (solar wind plasma; sources of the solar wind; instruments and techniques)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Simultaneous observations of the slow solar wind off the southeast limb of the Sun were made in May 1999 using optical measurements from the C2 and C3 LASCO coronagraphs on board the SOHO spacecraft and radio-scattering measurements from the MERLIN and EISCAT facilities. The observations show the slow solar wind accelerating outwards from 4.5 solar radii (R), reaching a final velocity of 200–300 km s-1 by 25–30 R. The acceleration profile indicated by these results is more gentle than the average profile seen in earlier LASCO observations of larger scale features, but is within the variation seen in these studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-000-0995-9
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  • 2
    Electronic Resource
    Electronic Resource
    The Solar Minimum Active Region 7978, Its X2.6/1B Flare, CME, and Interplanetary Shock Propagation of 9 July 1996 (1998)
    Springer
    Solar physics 181 (1998), S. 159-183 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio observations of the type II shock, and GOES disk-integrated soft X-ray flux during an extended period that included energy build-up in this active region. The LASCO coronagraphs measured a significant coronal mass ejection (CME) on the solar west limb beginning on 8 July at about 09:53 UT. The GOES 8 soft X-ray flux (0.1–0.8 nm) had started to increase on the previous day from below the A-level background (10-8 W m-2). At the start time of the CME, it was at the mid-B level and continued to climb. This CME is similar to many events which have been seen by LASCO and which are being interpreted as disruption of existing streamers by emerging flux ropes. LASCO and EIT were not collecting data at the time of the X-flare due to a temporary software outage. A larger CME was in progress when the first LASCO images were taken after the flare. Since the first image of the 'big' CME was obtained after the flare's start time, we cannot clearly demonstrate the physical connection of the CME to the flare. However, the LASCO CME data are consistent with an association of the flare and the CME. No eruptive filaments were observed during this event. We used the flare evidence noted above to employ in real time a simplified Shock-Time-of-Arrival (STOA) algorithm to estimate the arrival of a weak shock at the WIND spacecraft. We compare this prediction with the plasma and IMF data from WIND and plasma data from the SOHO/CELIAS instrument and suggest that the flare - and possibly the interplanetary consequences of the 'big' CME - was the progenitor of the mild, high-latitude, geomagnetic storm (daily sum of Kp=16+, Ap=8) on 12 July 1996. We speculate that the shock was attenuated enroute to Earth as a result of interaction with the heliospheric current/plasma sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016522812668
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  • 3
    Electronic Resource
    Electronic Resource
    Origin of strong interplanetary shocks (1985)
    [s.l.] : Nature Publishing Group
    Nature 314 (1985), S. 137-140 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Observations of 900 radio sources have been used to study the shape and motion of large-scale interplanetary transients associated with shock disturbances at 1 AU. The variations of plasma density and speed and the zones in the solar atmosphere from which the transients originate suggest ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/314137a0
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  • 4
    Electronic Resource
    Electronic Resource
    Solar particles seen by ulysses near 33°S (1996)
    Springer
    Astrophysics and space science 243 (1996), S. 199-202 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of a particle event (electrons 〉40 keV; ions 〉50 keV) at heliographic mid-latitudes are presented. The particles are shown to originate from an apparently insignificant solar source and to be stored prior to release into the solar wind.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644055
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  • 5
    Electronic Resource
    Electronic Resource
    Co-rotating particle enhancements out of the ecliptic plane (1995)
    Springer
    Space science reviews 72 (1995), S. 327-330 
    Details
    ISSN: 1572-9672
    Keywords: Heliosphere ; Energetic particles ; co-rotating interaction regions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The characteristics of the recurrent electron (38–53 keV) and ion (〉∼0.5 MeV) enhancements observed by Ulysses from mid-1992 to April 1994 are presented. The magnitude of the ion flux increases reached a maximum at a latitude of ∼20°S and decreased afterwards by ∼23%/degree until early 1994. The magnitude of the electron increases showed a similar trend until May, 1993, after which time it became approximately constant, until it started to increase again in early 1994. The electron enhancements have lagged the protons by up to 5 days once Ulysses left the heliospheric current sheet (mid-1993). The electron spectral index tended to harden (a) during the decay of the event and (b) as the latitude increased, up to 50°S. The events have recurred on a 26.0 day period, but with significant phase shifts over the 25 rotations studied. The H/He ratio decreases across the maximum intensity. The mean minimum value for H/He was 3.5±0.3, lower than that measured in previous studies in the ecliptic plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768799
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  • 6
    Electronic Resource
    Electronic Resource
    Solar particles observed near 33° S latitude (1995)
    Springer
    Space science reviews 72 (1995), S. 331-334 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have analysed the ions and electrons seen by the HI-SCALE instrument on the Ulysses spacecraft in the interval from 21–30 June 1993, ahead of an arrival of the CIR which has dominated the particle environment of Ulysses since July 1992. These particles show velocity dispersion effects usually associated with solar-flare particles. There was no flare activity of any consequence on the region of the Sun to which Ulysses was connected. We do however find a newly emerged active region (# 7525) close to the estimated site of connection, which we conclude could be the particle source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768800
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  • 7
    Electronic Resource
    Electronic Resource
    The Relationship of Green-Line Transients to White-Light Coronal Mass Ejections (1997)
    Springer
    Solar physics 175 (1997), S. 699-718 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report observations by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft of three coronal green-line transients that could be clearly associated with coronal mass ejections (CMEs) detected in Thomson-scattered white light. Two of these events, with speeds 〉25 km s-1, may be classified as ‘whip-like’ transients. They are associated with the core of the white-light CMEs, identified with erupting prominence material, rather than with the leading edge of the CMEs. The third green-line transient has a markedly different appearance and is more gradual than the other two, with a projected outward speed 〈10 km s-1. This event corresponds to the leading edge of a ‘streamer blowout’ type of CME. A dark void is left behind in the emission-line corona following each of the fast eruptions. Both fast emission-line transients start off as a loop structure rising up from close to the solar surface. We suggest that the driving mechanism for these events may be the emergence of new bipolar magnetic regions on the surface of the Sun, which destabilize the ambient corona and cause an eruption. The possible relationship of these events to recent X-ray observations of CMEs is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004981125702
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  • 8
    Electronic Resource
    Electronic Resource
    First View of the Extended Green-Line Emission Corona At Solar Activity Minimum Using the Lasco-C1 Coronagraph on Soho (1997)
    Springer
    Solar physics 175 (1997), S. 667-684 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The newly developed C1 coronagraph as part of the Large-Angle Spectroscopic Coronagraph (LASCO) on board the SOHO spacecraft has been operating since January 29, 1996. We present observations obtained in the first three months of operation. The green-line emission corona can be made visible throughout the instrument's full field of view, i.e., from 1.1 R⊙ out to 3.2 R⊙ (measured from Sun center). Quantitative evaluations based on calibrations cannot yet be performed, but some basic signatures show up even now: (1) There are often bright and apparently closed loop systems centered at latitudes of 30° to 45° in both hemispheres. Their helmet-like extensions are bent towards the equatorial plane. Farther out, they merge into one large equatorial ‘streamer sheet’ clearly discernible out to 32 R⊙. (2) At mid latitudes a more diffuse pattern is usually visible, well separated from the high-latitude loops and with very pronounced variability. (3) All high-latitude structures remain stable on time scales of several days, and no signature of transient disruption of high-latitude streamers was observed in these early data. (4) Within the first 4 months of observation, only one single ‘fast’ feature was observed moving outward at a speed of 70 km s-1 close to the equator. Faster events may have escaped attention because of data gaps. (5) The centers of high-latitude loops are usually found at the positions of magnetic neutral lines in photospheric magnetograms. The large-scale streamer structure follows the magnetic pattern fairly precisely. Based on our observations we conclude that the shape and stability of the heliospheric current sheet at solar activity minimum are probably due to high-latitude streamers rather than to the near-equatorial activity belt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004948913883
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  • 9
    Electronic Resource
    Electronic Resource
    Lasco Observations of Disconnected Magnetic Structures Out to Beyond 28 Solar Radii During Coronal Mass Ejections (1997)
    Springer
    Solar physics 175 (1997), S. 685-698 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two coronal mass ejections have been well observed by the LASCO coronagraphs to move out into the interplanetary medium as disconnected plasmoids. The first, on July 28, 1996, left the Sun above the west limb around 18:00 UT. As it moved out, a bright V-shaped structure was visible in the C2 coronagraph which moved into the field-of-view of C3 and could be observed out to beyond 28 solar radii. The derived average velocity in the plane of the sky was 110 ± 5 km s-1 out to 5 solar radii, and above 15 solar radii the velocity was 269 ± 10 km s-1. Thus there is evidence of some acceleration around 6 solar radii. The second event occurred on November 5, 1996 and left the west limb around 04:00 UT. The event had an average velocity in the plane of the sky of ∼54 km s-1 below 4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km s-1. In both events the rising plasmoid is connected back to the Sun by a straight, bright ray, which is probably a signature of a neutral sheet. In the November event there is evidence for multiple plasmoid ejections. The acceleration of the plasmoids around a projected altitude of 5 solar radii is probably a manifestation of the source surface of the solar wind.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004994214697
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  • 10
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    The Extended Solar Cycle Tracked High into the Corona (2012)
    Springer
    Details
    Publication Date: 2012-10-16
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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