Groundbased allsky imaging of gravity waves and ionospheric depletions

1
Ground-based all-sky imaging of gravity waves and
ionospheric depletions

• A small, compact, ground-based imaging system
  that will autonomously collect all-sky images of
  gravity waves and ionospheric depletions.

2
An all-sky imager for IHY

• We propose to develop an imager that will have
  selectable filters allowing the use of the same
  instrument installation for different purposes
  i.e. imaging atmospheric gravity waves,
  ionospheric depletions, and auroral activity.
  Multiple imagers could be used for tomographic
  imaging of airglow features two or more imagers,
  imaging the same feature in their overlapping
  fields of view give spatial and temporal
  information as well as velocity.

3
Space Weather Requirements

• All-sky imagers provide much needed space weather
  data.
  
• The system proposed here would use 3 standard
  filters 427.8 nm, 557.7nm , 630.0nm
  
• While the most common form of an all-sky imager
  is an auroral imager, there are two different,
  important applications of this technology.
  
• The first is a gravity wave imager. The optical
  signatures range from the UV through the near IR.
  In this application the CCD will have to be
  cooled.
• The second is imaging ionospheric structures
  (enhancements and depletions). The optimal
  signature for this is the atomic oxygen line at
  630 nm.

4
The Importance of Gravity Waves

• Gravity waves carry momentum and energy from the
  troposphere to the middle and upper atmosphere.
  
• Gravity waves can modify the behavior of the
  tides in the middle atmosphere and are
  responsible for the large departure of the middle
  atmosphere from radiative equilibrium and the
  production of the summer mesopause temperature
  minimum (the coldest place on Earth) where polar
  mesospheric clouds are found.
• The gravity waves also cause a "drag" on the
  polar front jet stream, which affects the
  development of cyclones and anticyclones and
  thus, the weather on the surface.

5
Ionospheric Irregularities

• Ionospheric irregularities exist in the low
  latitude ionosphere as large changes in the
  spatial distribution of the total ion density.
  
• The feature may take the form of a few large
  scale depletions or it may appear as many small
  depletions.
  
• We do not know what controls the different
  appearance of structure but they are correlated
  with radio scintillation.

Signatures of irregularities observed from an
imager, like that proposed here, in Hawaii.
6
Imaging ionospheric irregularities
complementary approaches

• A ground-based all-sky imager looks along the
  field lines to observe ionospheric irregularities
  by imaging in the oxygen 630 nm nightglow
  emission features and produces the time history
  of the irregularities.

• The TIMED/GUVI instrument images small-scale
  ionospheric irregularities from space but it
  takes a day to produce a full global map at one
  local time.

7
Instrument Design Outline

• Ground based imagers have been a common
  aeronomical tool for more that 50 years.
  
• A system for airglow imaging can be an all-sky
  design or a narrow field of view (FOV) imager (10
  20 deg) depending on the application.
  
• Our design will use commercial CCD cameras with
  standard photographic lenses to produce an imager
  with up to 70 deg FOV.
  
• The camera will be read out by their USB
  interface to a PC for storage.
  
• The PC will host interactive (Java-based)
  software for the display of the images locally
  and will upload the images to th internet for
  inclusion in the IHY Virtual Observatory.

8
Estimated Costs

• Development work
• 100K for software and hardware development
• Reproduction costs
• Camera head, lenses and interface less than 3K
  per copy