Time Line August 1998 Sun-Earth Connection Event Time Line August 1998 Sun-Earth Connection Event

Time Line August 1998 Sun-Earth Connection Event

Aug. 24, 22 UT, X1/3B SOLAR FLARE

A solar flare (solar eruption) X1/3B occurred at active region N35E09 (essentially central meridian, and North on the face of the Sun). It was monitored by the geoenviromental satellites GOES soft X-ray instrument. 2205 UT, Intense Type III radio bursts produced by solar flare, observed by WIND/WAVES. 2204-2350 UT, Meter/Decameter Type II radio bursts are reported at Culgoora and at Sagamore Hill Radio Astronomy Observatories (they indicate shock velocities in the thousands of km/s). Event is strong and produces high fluxes of protons >10 and >30 MeV. The fluxes keep climbing with time, a signature of strong outward propagating shock. 2215-2400 ISTP WIND WAVES sees very intense decameter type II radio bursts, by the end of the day at 0.5 MHz. These radio emissions have a nearly constant drift in frequency, which suggest an IPS propagating away from the Sun with a velocity between 1000 and 2000 km/s.

Aug. 25 0000 to Aug. 26 0620

ISTP WIND/WAVES observes very intense clear cut kilometric Type II radio emissions, which depending on the assumption on the type of the source gives a propagation velocity of approximately 1500 km/s. NRT ACE/EPACT and WIND/EPACT observe climbing fluxes in the 1-2 MeV particles, a clear signature of a shock heading on toward Earth. NRT ACE/SIS observes intense nearly constant fluxes of energetic 10 and 30 MeV ions. GOES soft X-ray spectra is still dominated by the slow decrease in photon intensity from the August 24, 22 UT flare.

Aug. 26 0620 UT (SHOCK at 250 RE from Earth)

NRT ACE/EPACT shows strong interplanetary shock (IPS) in solar wind plasma and magnetic field data. This is 32 hours transit time for the shock, i.e. an approximately transit velocity of 1300 km/s from Sun to Earth.

0636 UT (SHOCK at 115 RE from Earth)

ISTP WIND/SWE and WIND/MFI record strong interplanetary shock (IPS) in plasma and magnetic field data. [ Preliminary estimate of the shock velocity in the vicinity of the Earth, assuming frontal propagation toward Earth. Under these assumption we used the observation of the IPS with ACE and WIND and the time and location of ACE and WIND, with the result of a velocity of propagation of the IPS shock of 917 km/s] ISTP WIND/WAVES sees very intense type II radio bursts ending at shock. NRT ACE/EPACT, NRT ACE/SIS, WIND/EPACT show very intense energetic particles spike-like flux increases at shock, from tens of keV to tens of MeV NOAA provisory global geomagnetic Kp index changes from 2 to 5 (A sign of change in the geomagnetic conditions from calm to disturbed) Aug. 26, 14 UT ISTP WIND/SWE NRT data gives SW velocity V of 700 km/s, proton density Np 4 to 5 part/cc, and thermal velocity Vth of 100 km/s. ISTP NRT WIND/MFI data gives an IMF magnitude of approx. 12 nT, oscillating fields. Aug. 26, 16 UT ISTP NRT WIND/SWE data gives V climbing to close to 800 km/s, IMF close to 15 nT. Aug. 26, 18 UT NRT ACE/SWEPAM data gives SW V above 800 km/s. Aug. 26, 22 UT NRT ACE/SWEPAM data gives a SW V close to 900 km/s, possibly the peak SW velocity during this Sun-Earth connection event. NRT ACE/MAG data shows that the interplanetary magnetic field (close to 20 nT) turns almost completely south.

Aug. 26, 22 UT to Aug. 27, 2350 UT, One Whole Day of IMF South

NRT ACE/MAG and ISTP WIND/ magnetometers show that the interplanetary magnetic field stays put south for more than 24 hours except for a sharp rotation near 02 UT to dawnward on Aug. 27.

Aug. 27, 0140 UT and 1015 UT, Images of Auroras at Mid-Latitudes

ISTP POLAR/VIS shows at 0142 UT auroras extending southward of the great-lakes region of the USA. At that time ISTP POLAR/UVI looks to the north atlantic region and shows intense auroras, in the UVI frequencies, extending southward from Iceland. Later, at 1016 UT ISTP POLAR/UVI shows auroras over the continental territory of the USA.

Aug. 27, 00 to 12 UT, Severe Geomagnetic Disturbances

During the first twelve hours on Aug. 27 the Kp index is 7 or above, in its logarithmic scale from 0 to 9.

Aug 28, 1998

NOAA provisory global Kp index becomes smaller than 5 indicating a transition from strongly disturbed to unsettled geomagnetic conditions.


Last updated: Sep. 8, 1998