Section homepage | Observations

NLC observations 1997

Report by Veikko Mäkelä

Ursa Atmospheric Optics Section have recorded NLC observations since early 1980's. Earlier the observations have been published in paper reports. Since 1989 Reports have been published only in Ursa Minor bulletin of Ursa sections.

The summer 1997 was rather successful, even there were only seven observers. July 1997 was one of the most active months in the history of the section. 22 display were detected, 4 nights were negative and 5 without observations. During Aug 1-16 there were still 7 displays. Unfortunately June was poorly observed, partly due to the lights skies in the most parts of Finland.

With verbal description, some numeric estimations have been used:

W	wideness	(1-5, 1=single forms, 5=all-sky)
I	intensity	(1-5, 1=faint, 5=remarkable bright)
S	structures	(I=veil, II=bands, III=billows, IV=whirls, 0=unknown, unclassified, S="knots", P="crossing streaks", V="net-like")
r	reliability	(0=unsure,1=quite sure, 2=sure)

Observers

Name              Code   Sites                         obs  neg

Jani Katava       KAT    Helsinki, Raisio               3    1
Tomi Lyytikäinen  LYY    Helsinki                       3    -
Olli Manner       MAN    Helsinki                       3    -
Veikko Mäkelä     MAK    Helsinki, Hämeenlinna          4    2
Pekka Parviainen  PAR    Kustavi, Turku, Paimio        14    -
Leo Rajala        RAJ    Jämsä                         18    7
Teemu Öhman       ÖHM    Oulu, Äänekoski, Hämeenlinna   6    -

obs = NLC displays, neg = negative observations

June | July | August

27/28.6.

W=2, I=3, S=II+IV, r=2
Small display with two small areas. Bands in both areas.
MAK,RAJ

1/2.7.

W=3, I=4, S=I+II+III+IV, r=2
Quite a large NLC area. Some billows, which disappered later. One strong whirl and band structure. Top brightness was 4 (1-5).
LYY, RAJ

2/3.7.

W=3, I=2, S=I+II, r=1
About 60 degrees wide area with veil and bands. Few bands also in eastern sky. Intensity was low maybe due to light sky.
RAJ

5/6.7.

NEG, r=1
MAK

6/7.7.

W=3, I=3, S=I+II, r=1
About 90 degrees wide area. Veil+band type display. The brightest structure was a strong band (I=4).
MAN,PAR

7/8.7.

W=2, I=2, S=0, r=1
50 degrees wide area with undefined structures. Quite faint display. The weather conditions were poor.
PAR

8/9.7.

W=3, I=4, S=I+II+III+IV, r=2
Display mainly in the western sky from all the thre observers. Band+billow type structure, bright billow observed by Parviainen and Lyytikäinen. The top intensity was 4. The stereo photographing by Parviainen.
KAT,LYY,PAR

11/12.7.

W=4, I=5, S=I+II+III+IV+S+P, r=1
Bright display detected only by Lyytikäinen (perhaps cloudy in other sites). Wide area, all the structures. Dominating forms were bands and strong whirl. Yellowish and brownish color also observed.
LYY

12/13.7.

W=4, I=3, S=I+II+III+S+P, r=1
A half-sky display by Rajala (30 degrees over zenith). Manin band type display, with "knots" and crossing streaks. Also some billows existed. Fast motion to northwest.
RAJ

13/14.7.

W=4, I=4, S=I,II,III,IV,S,P, r=2
As large as the night before. Bands were directed SE-NW. Very active and dynamics display with sharp edged bands and strong whirled area. Some herring-like structures and billows, too. The motion westwards or northwestwards.
MAN,PAR,RAJ

14/15.7.

W=1, I=4, S=II+0, r=2
The fourth night with NLC. Small area display in north with band type structure. Two bright yellowish patches reported by Mäkelä. The NLC disappeared about 1:00 local daylight saving time.
KAT,MAK,PAR

15/16.7.

r=1
In the beginning of the night negative observations (KAT,MAK,RAJ). At 2:00 local time Manner report some NLC.
MAN,KAT,MAK,RAJ

16/17.7.

W=2, I=4, S=I,II, r=2
Some faint bands and veil. Area was first in NW-NE, later in east by Rajala. Some cloud distrubed observations.
MAK,PAR,RAJ

17/18.7.

W=2, I=3, S=I,II,III, r=1
Medium bright display with 70 degrees wide area. Sharp IIb bands as dominating structures in NW. Also some billow groups. Possible motion to NW.
RAJ

18/19.7.

W=2, I=2, S=II, r=1
Faint bands in NNW. The observations were interrupted by clouds.
RAJ

19/20.7.

W=4, I=3, S=I,II, r=2
Mainly western sky display with quite a large are (up to 50-60 degrees by Mäkelä and Öhman, over zenith by Rajala). Mainly band type display, some billow observed by Öhman. Top intensity 3.
MAK, PAR, RAJ, ÖHM

20/21.7.

NEG, r=1
RAJ

21/22.7.

NEG, r=1
RAJ

22/23.7.

W=2, I=3, S=I,II,III, r=1
40 degrees wide band+billow area in N. The brigthnees increased (max. I=3) to 1:00 local time, then the NLCs disappered.
PAR

23/24.7.

W=4, I=3, S=I,II,III,IV, r=1
Quite a large display, upper limit almost in zenith. Veil, bands and billows. In the midnight strong band with crossing streaks. Later the band disappered, streaks were left. Motion to SW. The intensity decreased at 1:00, probably due to Earth's shadow.
RAJ

24/25.7.

W=2, I=3, S=II,III, r=1
Bands and billows. Brightness mainly 3, but few bands brightened up to value 5 for a moment. Motion southwards. There were some cloud disturbance in observation.
PAR

25/26.7.

W=3, I=3, S=I,II,III, r=1
Veil+bands and strange lenticularis like billows or patches. They were quite regular sized (0,5x3-4 and 0,5x1-2 degress). The intensity was 2-3 and the area width about 70 degrees.
RAJ

26/27.7.

W=2, I=3, S=II,III, r=1
Fifth night with NLC in row! In the beginning faint, later medium bright bands and billows. There was cloud disturbance in observation.
PAR

28/29.7.

W=2, I=4, S=I,II,III, r=1
Poor observing conditions. Some rather bright band+billow structures were visible throught cloud caps.
RAJ

29/30.7.

W=2, I=1, r=1
Some unindentified faint NLC forms. Clouds disturbed observations.
PAR

30/31.7.

W=3, I=3, S=I,II,IV,0, r=2
The observing conditions were poor in both sites. Some veil and unsharp (IIa) bands was observed. Rajala reported also whirl structures and some unclassified NLC forms. The reports of the both observer are made about different NLC areas. The intensity was 3.
PAR,RAJ

31.7./1.8.

NEG, r=1
RAJ

1/2.8.

W=3, I=2, S=I,II, r=1
Rather faint veil+band type display. The area was small, 20 degress wide in low altitude in N.
RAJ

3/4.8.

W=2, I=2, S=II, r=1
A little unsure case. Some bands in NE.
ÖHM

4/5.8.

NEG, r=1
< RAJ

5/6.8.

NEG, r=1
RAJ

6/7.8.

W=2, I=2, S=I,II,III, r=2
Veil and bands between N and NE. Later the area expanded northeastwards (due to Earth's shadow?). Later there were also billows. The intensity were low (I=2).
PAR, RAJ

8/9.8.

W=3, I=3, S=I,II, r=2
Veil and bands. In Raisio, Southwestern Finland Katava observed 20 degrees wide bluish area with veil. The intensity was low in the beginning, but the display brightened later.
KAT,RAJ,ÖHM

9/10.8.

NEG, r=1
< RAJ

10/11.8.

W=4, I=4, S=I,II,III,IV,S,P, r=2
The display with many structures (veil, bands, whirl, "knots" and "streaks"). Billows were reported by Öhman. In the midnight the display were low in the north, but in the morning, 4:00 local time, the areas expanded as an all-sky display. The top intensity was I=4.
PAR, RAJ, ÖHM

13/14.8.

W=3, I=4, S=I,II,III, r=1
Quite a nice display. Some medium bright NLC (veil, bands and billows). There were also some brighter points in NLC forms.
™HM

16/17.8.

W=2, I=4, S=II, r=1
The last reported NLC display in 1997. 20 degrees wide group of bands. it brightened up to I=4 (probable this was contrast effect between dark sky and NLCs).
RAJ, ÖHM

Section homepage | Observations