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Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William Rogers e-mail: [email protected]
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Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Oct 19, 2020

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Page 1: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Detecting ThermalsRemotely:

Initial Results

Nilton Renno, Stephen Rogacki,Michael Parker, Brian Russell, RobbGillespie, and William Rogerse-mail: [email protected]

Page 2: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Outline• Fair weather electric fields

– The global electric circuit– Electric field in thermals

• Previous investigations• Theoretical predictions

• Our new electric field sensor• Measurements

– From the ground– Airborne

• Conclusions

Page 3: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Fair weatherelectric fields

Page 4: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

The global electric circuit

+ + + + + + + + + + + + + + + + + + +

- - - - - - - - - - - - - - - - - - - - - - - -

2 pA/m2

500 kV

~ 100 lightning strikes per sec

Ionosphere

Surface

I

Page 5: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Electric fields in thermals

- - - - - - - - - - - - - - - - - - - - - - - -

+ + + + + + + + + + + + + + + + + + +

+ + - + + + + - + + - + + + +

- + - + ++ + + +

EE

Page 6: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Results of previousinvestigations

Markson, 1975see also Kohl, 1968

Page 7: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Theoretical predictions

• Assuming that thermals are uniformlycharged (-100 e/cm3), infinitely longcylinders of ~100 m of radius, we get

where d is the distance from the thermal (in m).

• Thus, the electric field at 1 km from thethermal is ~10 V/m.

E !10

4

d

V

m

Page 8: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Our new electricfield sensor

- -- - -- -

- - -- - -- - - -- - --- - -+ + + +

Page 9: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Requirements• To distinguish the ambient space field

from the effects of charged particlescolliding with the sensor– Vary the rotation rate during measurements

(Maruvada et al. 1983)– Add sharp points to limit the sensor potential

• To measure the electric fields ~ 1 cm fromthe surface– Instrument diameter ~ 1 cm

Page 10: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Our sensor(patent pending)

Page 11: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Sensor characteristics• DC to > 10 Hz• Range: 1 to 106 V/m• Resolution: 1 V/m• 2-d vector field (plane of rotation)

• A version of the sensor for gliders might bedeveloped– The idea of installing it inside a winglet or the fin

might be studied

Page 12: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Installation on EP

Page 13: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

horizontal plane

vertical plane

Measurements

relative to the glider

Page 14: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Measurements at theground

Page 15: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Ground MeasurementsMay 28, 2008

from 14:16:25 to 16:11:00 local time

1 2 3

1 2 3

321Thermals selected for study

Page 16: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Flights at the TuSC inArizona

Page 17: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Flight Path July 02, 2008

12

Page 18: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

July 02, 2008Start of flight End of flight

1 2

Page 19: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

July 02, 2008Thermal #1

~ 2 km

Page 20: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

July 02, 2008Thermal #2

~ 1 km

Page 21: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Flight path July 04, 2008

Page 22: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

July 04, 2008

1 2

Page 23: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

July 04, 2008 Thermal #1

~ 1.2 km

Page 24: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

July 04, 2008Thermal #2

Page 25: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Conclusions

Page 26: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

• These were our first measurements– There were problems with the direction of the e-field– The frame of reference was the glider

• Theory and our initial measurementssuggest that thermals can be detectedremotely with a passive electric field sensor– The signal is much larger than the sensitivity of the

sensor

• The 60 s average electric field increasessteadily toward thermals– The first derivative of the electric field might be a

good indicator of the approach of a thermal– The direction of the local field might be a good

indicator of the direction of the thermal

Page 27: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

• There are theoretical andobservational indications that theelectric field contain informationabout the nature (e.g., dust andmoisture content) of the local air-mass– It might contain information about regional

circulations (shear lines, organization ofthermals, sea breezes, etc)

– This will be investigated

Page 28: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Plans for the future

• Additional measurements will beconducted:– In an inertial frame of reference– Including the direction of the electric field– In various regions and weather conditions

• The position of the glider with respectto the thermals will be analyzed– The idea of using the electric field to locate

(find the direction) the thermals will be tested

Page 29: Detecting Thermals Remotely: Initial Results · Detecting Thermals Remotely: Initial Results Nilton Renno, Stephen Rogacki, Michael Parker, Brian Russell, Robb Gillespie, and William

Thanks!