What do we know so far
(Preliminary DRAFT)
[Based mainly on study of the 27 March 2017 event at this stage]
[To be reorganised into set of observable parameters for consistent study of all events]
[to be represented as interpretations/conclusions within relational database]
Observations
· By camera mostly
· Several visual sightings reported
· Observed 19? times from 2013 by 40? photographers
· Multiple times for several events
- Multiple occurances per event?
· From mid-latitudes
· Mostly across southern Australasia
· Few photos submitted from Europe and North America
Timing
· Night time
· During heightened geomagnetic activity
o Or only because photographers out photographing aurora
· Timeline (required)
Duration
· Observer up to 45mins
Color and Hue:
Very faint dark blue in photographs
Consistent
Form
· More evident with photo enhancement
· Ray-like in serval bundles of varying height
· Tilts towards Eastern Australia
Extent and Height:
· Extends beyond frame of most superwide lens views
· Most prominent event 27 March 2017 being studied
· Triangulation measurement
o From locations across southern Australia
o Base placed over the night side of the Antarctic Circle.
· Several other events suggest the same applies for the Artic.
· Mapping
o By astrometric calibration and analysis of astronomical (wide angle) photos
o Conforms to known Earth’s magnetic field lines
o Curves slightly away from pole
· Reaches beyond 10,000kms in height
· Width differs with view location/line, but in order of a few hundred kilometres.
Dynamics
Understood from
o Timelapse photography
§ Synchronised from different locations
o Image processing
o Tone profiling
· Consistency
o Colour
o Generally maintains shape features
· Changes slightly over time
· Appears to rotate
o Anti-clockwise
o Southern hemisphere only?
o Dependant on conditions?
· Drifts slightly westward
· May also drift poleward
· Lowish tilt inclining towards upright
· Hight increases
· Sequence
· Faint and more diffuse at start
· Becomes bigger and more discrete
· Slightly lessens in height and fades
Environmental correlations:
· Full study of all events required
o Circumstances and conditions may not be prevailing.
o So far here are some common correlations
· During geomagnetic disturbances
· From coronal hole
o More disturbed solar wind
· During/after falling DST
· After sub-storming
o But could also be during some minor ones
Aural oval relationship
· Apparent alignment with inner edge of auroral oval
· Aligns lengthwise towards centre of aural oval
· During brief poleward contraction stage of auroral oval
o Contracts and power minimises from Ovation Prime
Ionosphere conditions
· Joule heating - almost stops and abruptly then gradually increases
· Magnetosphere conditions
· Field aligned currents - positive and negative tend to neutral
· Electric potential - extent reduces and tends neutral
· Open/closed field lines - boundary appears to be in GBR vicinity
· Closed field lines - extend deep into tail
· Velocity increases partway into tail
Solar wind
· From OMNIWeb
· Generally positive Bz at ACE/DSCOVER
· Elevated solar wind speed
o Generally increasing with slight ramp up and down
· Proton density - slight fluctuation
· Proton temperature - generally decreasing with sudden disturbed step up
Solar wind at bow shock
· Bz - +ve - to -ve drop after period of slightly negative flucations
· Bx - generally increasing
· By - +ve - to -ve drop after period of slightly positive fluctuations
DST – disturbance
· SYM/D /H - +ve recovery(???) form long period of decline
· SYM/H - -ve drop after period of -ve fluctuations.
Electric field
· +ve ramp up and down after period of +ve to -ve
Flow pressure
· Step up after long period of easing
Ion drift
· From DMSP-16
· Significant vertical and horizontal ion drift for several minutes reaching -5000m/s