Archives for Tony

Solar wind summary


The solar wind environment at the ACE spacecraft was nominal. Wind
speed remained in the mid 300 km/s range. Bt was less than 6 nT for
most of the period and Bz never dropped below -4 nT. The Phi angle was
mostly negative (toward). A small discontinuity was observed around
25/0350 UTC when wind speed increased from around 320 to 360 km/s and
Phi shifted slightly toward positive.

25th October


Tonight’s estimated aurora level:

Level 4 – High (with chance of G1 storm levels)

Forecast:
Auroral activity will be at high levels. Weather permitting, aurora displays will be visible overhead or on the horizon in Trondheim (Norway), Vaasa (Finland), Sundsvall (Sweden) and Faeroe Islands.

Comments:
CME’s that were due to arrive around midnight last night are late. It is probably a good thing for European aurora watchers as now the CME’s are expected to arrive this evening when the auroral oval will be in a more favourable position. Although they can arrive any moment really, computer models predicting their arrival are not right too often. The prediction is still that they could spark G1 storms, but until they arrive we just don’t know. 3 cme’s arriving at the same time is pretty rare.

24th October


Solar activity was high. The largest flare of the period came from Region 1877 (S12E04, Dkc/beta-gamma-delta). An impulsive M9/1n (R2 – Moderate on the NOAA Scale) erupted at approximately 24/0030 UTC and was associated with Types II (est. speed 1321 km/s) and IV radio emissions. This region increased in area and maintained a delta in its intermediate spots. Region 1875 (N08W16, Ekc/beta-gamma-delta) continued to be the most active region, producing multiple C-class flares as well as several impulsive M-class (R1 – Minor on the NOAA Scale) flares during the period. These included an M2 at 23/2053 UTC, an M1 at 23/2343 UTC, an M3 at 24/0016 UTC, another M2 at 24/1009 UTC, and another M3 at 24/1033 UTC. This region maintained a beta-gamma-delta magnetic configuration, mainly in the intermediate spots. Yet another faint full-halo CME, associated with the M9/1n flare at 24/0030 UTC, was observed in Lasco C2 imagery at approximately 24/0148 UTC. Analysis is in progress to determine the possible impacts at Earth.

Solar wind summary


Solar wind speeds ranged from a maximum of approximately 360 km/s to a
minimum of just under 300 km/s as weak coronal hole high-speed stream
(CH HSS) effects continued to wane. IMF Bt remained steady near 5 to 7
nT over the period. IMF Bz remained mostly positive with only very brief
intermittent negative decreases to as low as -3 nT. IMF Phi remained in
a primarily negative (toward) orientation for the majority of the
period, with brief transitions to positive (away) early in the period.
Ace EPAM indicated a slight enhancement across a few of the lower energy
channels at the time of the brief sector change but decayed to
background levels later in the period.

24th October


Tonight’s estimated aurora level:

Level 3 – Medium (with potential for level 5)

Forecast:

Auroral activity will be at medium levels. Weather permitting, aurora displays will be visible overhead or on the horizon in Mosjøen (Norway), Oulu (Finland), Luleå (Sweden) and Reykjavik (Iceland).

Comments:

The geomagnetic field is expected to be at predominantly quiet levels through midday on day one (24 Oct), before the anticipated onset of effects from three glancing blow CMEs observed leaving the Sun between 20 and 22 Oct. Initial geomagnetic impacts of the transients are expected to be in the form of unsettled conditions late on day one with an increase to conditions as high as minor storm (Kp5/NOAA Scale G1-Minor) in the early hours on day two (25 Oct). A recovery to unsettled levels, with possible isolated active conditions, can be expected for day three (26 Oct) as conditions wane prior to the arrival of the fourth CME of the past few days, which is expected to also be weak and arrive outside of the forecast period.

23rd October


Tonight’s estimated aurora level:

Level 2 – Low

Forecast:
Auroral activity will be at low levels. Weather permitting, aurora displays may be visible overhead or on the horizon in Bodø (Norway), Sodankylä (Finland), Kiruna (Sweden) and Reykjavík (Iceland).

Comments:
The geomagnetic field is expected to be at predominantly quiet levels for the remainder of day one (23 Oct) and the first half of day two (24 Oct), before the anticipated arrival of three of the CMEs. Initial geomagnetic impacts of the transients are expected to be in the form of unsettled conditions late on day two and increase to conditions as high as active (less than NOAA Scale G1 (Minor)) in the early periods on day three (25 Oct.)

 

Solar wind summary


Solar wind speeds continued a somewhat unstable climb throughout the
period in response to the likely delayed onset of anticipated weak
coronal hole high-speed stream (CH HSS). Speeds began the period near
320 km/s, then increased to a peak of just under 400 km/s before
dropping back down to the mid 300s by the end of the UT day. Another
slow rise occurred just after the beginning of the new day with a peak
near 390 km/s then a slow but steady decrease to end the period at
approximately 350 km/s. IMF Bt peaked near 9 nT at the beginning of the
period, but has steadily decreased to around 5 nT. IMF Bz was unstable
as well remaining mostly positive with intermittent decreases to near -5
nT. IMF Phi remained in a primarily negative (toward) orientation for
the majority of the period.

23rd October


Solar activity was moderate. Region 1875 (N09W05, Ekc/beta-gamma-delta)
continued to be the most active region, producing the vast majority of
the flare activity. It produced the two largest flares of the period, an
M1/Sf flare at 22/1520 UTC and an impulsive M4/1b at 22/2120 UTC. The M4
flare was associated with a 220 sfu Tenflare and a Type II radio sweep
(estimated shock speed 1955 km/s). This region continued to exhibit a
beta-gamma-delta magnetic configuration with separate deltas in its
trailer and intermediate spots. Region 1877 (S13E17,
Dki/beta-gamma-delta) decreased in area from 390 millionths to ~250
millionths, but developed a delta in its intermediate spots. It was also
responsible for a few low-level C-class flares throughout the period.

A faint, asymmetric full halo CME, associated with the M4/1b flare, was
observed in Lasco C2 imagery at ~22/2200 UTC. WSA Enlil analysis
indicates speeds of approximately 668 km/s with at least a portion of
the ejecta expected to impact the Earth early on 26 Oct. The current WSA
Enlil run has all four of the CMEs from the past three days included.

Solar wind summary


Solar wind speeds remained stable just under 300 km/s for the first half
of the period, then began a slow but steady increase to just under 340
km/s near the end of the period in response to the likely arrival of the
anticipated weak coronal hole high speed stream (CH HSS). IMF Bt began
the period near 3 nT, then increased slightly to 5 nT and ended the
period near 7 nT. IMF Bz was weakly positive for most of the period with
isolated decreases to approximately -5 nT. Phi remained in a primarily
negative (toward) orientation for the majority of the period.

22nd October


Tonight’s estimated aurora level:

Level 1 – Quiet

Forecast:
Auroral activity will be at quiet levels. Weather permitting, aurora displays may be visible overhead or on the horizon in Tromsø (Norway) and Utsjoki (Finland).

Comments:
The CH HSS is/was much weaker than predicted. So aurora activity will be quiet. There are two CME’s from 20 Oct that will brush past earth possible as early as tomorrow. So these events might spark auroras in Northern latitudes 65°N and above. But they are predicted to be quite weak. So for the rest of us 65° and below, we will have to wait for something more significant for an aurora show.