metal atoms observed in the thermosphere over arecibo
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Metal atoms observed in the thermosphere over Arecibo. Jonathan S. Friedman (SRI-AO) Xinzhao Chu (UCB–CIRES) Christiano Brum (SRI-AO) Steven M. Smith (BU) Jia Yue (NCAR ) (and many others). AO K Lidar – 12 March 2005. (Note the log scale). Layer descent rate is ~ 20 km/ hr , or ~ 6 m/s.

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metal atoms observed in the thermosphere over arecibo

Metal atoms observed in the thermosphere over Arecibo

Jonathan S. Friedman (SRI-AO)

Xinzhao Chu (UCB–CIRES)

ChristianoBrum (SRI-AO)

Steven M. Smith (BU)

JiaYue (NCAR)

(and many others)


ao k lidar 12 march 2005
AO K Lidar – 12 March 2005

(Note the log scale)

Layer descent rate is ~ 20 km/hr, or ~ 6 m/s


thermospheric k chemistry
Thermospheric K Chemistry

Neutralization production of K

  • d[K]/dt = 5×10-5/s  [e-] ~ 2×104/cc and
  • Ionosonde echoes  [e-] ~ 2×105/cc

recombination rate ≈ 10-11 cm3/s

K+ lifetime is ~240 hrs in a 2×105 e-/cc Es

Ionization loss of K

for O2k = 5.6 × 10-9 cm3/s

for NO k = 4 × 10-9cm3/s

K lifetime is ~140 hrs at 135 km.

K production exceeds loss by 25x


ionosonde measurements 7 ut
Ionosonde measurements, 7 UT



4 MHz

Plasma Frequency

The ionogram indicates the presence of a fairly strong Es layer. 4 MHz [e-] ~ 2×105/cc


til like properties of the layer
TIL-like properties of the layer
  • TIL a wavefront, and a 20 km/hr (6 m/s) wave would be consistent with a semidiurnal tide or gravity wave.(Chu et al. (GRL 2011 & SA44A-03) observed periodicity in the thermosphere over McMurdo and thus were able to establish the wave parameters related to the layer.)
  • TIL  Periodicity in the thermosphere.Upper mesosphere?


k integrated column above 110 km
K Integrated Column above 110 km



A hint at an enhancement at 04 UT (local midnight), 6-h wave?


wave modulation of k densities below 100 km
Wave modulation of K densities below 100 km



- An upward-propagating GW of period ca. 115 min is seen to reflect after 4 UT.

- Discontinuity in the profile centroid at 6:40 UT.


thermospheric neutral atom layer summary
Thermospheric Neutral Atom Layer Summary
  • The characteristics of the layer are similar to those of a tidal ion layer: Phase velocity, morphology, concentration.
  • There is a strong Es layer prior to the appearance of the thermospheric K layer.
  • Neutral K production and loss rates are reasonable.
  • The descent rate of ~6 m/s is slower than a typical tidal ion layer (~30 m/s). Does this allow time for the neutralization?

Note: Geomagnetic activity: Kp ≤ 1, low TEC.


  • We have presented what is, to our knowledge, the first observation of a neutral metal (K) atom layer extending above 150 km into the thermosphere.
  • It is likely the source of the K atoms is through radiative recombination of K+ within an Es layer.
  • The evidence indicates the occurrence of a strong, localized sporadic E layer with sufficient K+ content over a long enough lifetime to produce detectable K through radiativerecombination, although the altitude of the Es is unknown.
  • After many hundreds of nights, 1000s of hours over 12 years observing this event is unique. Why?